Speed Differences

 Speed is probably the single most overall important thing in vs debates. It's relevant for characters from very low tier to very high tier, and if you have a significant advantage, it is one of the hardest things to counters. With things like power there are more types of haxes that can get around that like regeneration, mind control, intangibility, and existence erasure. But a significant speed gap is hard to counter to the point that speed equalized is almost a rule on some sites. But what exactly is a "significant" speed gap, and how big a gap in speed can a character realistically fight? Well that depends on roughly three points: what other abilities the characters have, do either have reactions disproportionate to their speed in comparison to humans, and how precisely you know the speed gap is. I'd like to give an answer to this question going through these three factors individually.

Other Abilities and Speed Comparisons:

Obviously if two characters are identical clones, and you make one faster, than really ANY amount of speed boost is going to give them a better than average chance at winning because there is nothing else to compensate for it. On the other hand, if one character's passive presence would kill the other and the other has no way to get around it, no amount of speed advantage is going to really help. As such the degree of speed that is surmountable depends on what other abilities the two characters have. 

For the first scenario I'm going to be ignoring the other two factors so I can add them in later. So assume that both characters speeds are known exactly and the two character have proportionate reaction time to their speed in comparison to a normal human. In other words, if they can move twice as fast, they have a reaction time half as long. The average human speed is variable depending on walk, jog, run or sprint, as well as age and gender but for an easy round number we can use 3 meters per second, which is in roughly the correct running range, if somewhat conservative, of 2.9 to 3.6 meters per second. The average human reaction time in comparison is 0.25 seconds for visual stimulus.

So let's do some comparisons on what would be faster or slower than an average person to try giving an intuitive sense of what fighting someone with higher speed would be like:

1x (Identical Speed): When two people with essentially the same speed fight in real life, they can generally avoid each other strikes from anything other then very close, though this is actually due to pre-empting blows. The hand famously moves faster than the eye and the speed of a punch is fast enough to effectively blitz using two untrained humans but generally people are reacting to the motions people make when moving to throw a punch.

2x: 6 meters per second: This is about the general comfortable speed of a bicycle and on the other half average human running speed, 1.5 meters per second is upper end walking speed. So as you can tell it's a substantial difference. However it doesn't seem insurmountable by any means. Athletes it is said can generally run between 14 and 17 mph (6.25 to 7.6 meters per second) which means this is near the lower end of athlete speed. If you imagine an average person in a fight with a professional Runner, that is what a fight like this might look like, with the heighted reaction speed being much more the notable  feature here compared to the actual movement speed. At an average reaction speed of 0.25 seconds, a character moving 6 meters per second should be able to move 1.5 meters in one direction or 0.75 meters in two directions meaning that they should be able to strike first from an extended melee range (the range of humans with weapons) or punch from outside average punching range (0.635 meters) and exit before the opponent can punch back. 

3x: 9 meters per second: This is obviously much faster than the prior though is still slightly less then Olympic qualifying events, and is similar to how fast cars travel in residential areas, or in contrast it's similar to the difference between an average human running and an average human slowly walking. This is a fairly dramatic difference mostly due to the increased reactions. The faster character would be perceiving their opponent moving at 1/3rd normal speed meaning it would be hard to them even at melee range. Likewise with average human reactions of 0.25 seconds for visual stimulus, a character moving 9 meters per second would be able to reach them before they could react from a distance of 2.25 meters. This is outside the range of most melee weapons and suggests they could weave back and forth hitting and retreating if the opponent is limited to melee. A character like this could go back and forth over a meter before their slower foe could react, giving them an ability to hit outside melee range and retreat. This requires at least some level of abilities to counter, though I wouldn't think things more dramatic than large area of effects attacks.

4x: 12 meters per second: The top speed reached by a real world human is Usain Bolt's famous 12.42 meters per second. The average boxer punches at a speed of 25 mph or over 11 meters per second. This is also about the speed of a running housecat or dog. If the slower character has a notable advantage in power, mass and/or skill this is still not an insurmountable gap. There's a thought experiment often thrown around "who's win between Bruce Lee vs Usain Bolt" and while I think this is misused in a way to suggest very dramatic movement speed differences can be dismissed, at these limited human speeds, it's clear somewhat superior reaction speed, skill, and strength would easily eclipse a several factor large movement speed gap. Similarly a normal human would pretty easily beat a housecat or dog due almost entirely to the gap in mass and to a lesser extent the gap in skill/intelligence. Assuming the two characters are more similar in other stats, the faster character would be able to move 1.5 meters, nearly the length of a human being, back and forth before the other character could react. The faster character would perceive the slower character moving at a quarter speed, meaning their punch normally 15 meters per second would appear to be moving 3.75 meters per second, meaning it would seem to be someone punching at them at roughly their own run speed. This means even if the strike was a surprise, so long as it's not point blank, they would still likely be able to move out of the way. This is pretty notable as it means unless the slower character can attack disproportionately quickly, then they either need a surprise attack at almost point blank to hit the faster character or they need an attack that can't be dodged in order to get any kind of hit.

5x: 15 meters per second: This is superhuman speed, more akin to the speed of horses than humans. At 5x speed, a character could move 3.75 meters in one direction before the slower character could react, which would be the majority of an average room. This means that this speed a character could seem to just suddenly "appear" at any part of a small room the two characters were in, assuming they were agile enough to avoid any obstacles in the room. They would also be able to move upwards of 2 meters in two directions meaning they could hit an opponent with almost any melee weapon and move back before the opponent could counterattack. At 5x speed, the faster character would perceive their opponent moving at "relatively" 0.6 meters per second, and their punch would be seen as moving at 3 meters per second, the same speed as the faster character. In other words, this is the speed difference between how fast an average person can run and an average person can punch. It would be nearly impossible to hit a character this much faster with anything but a surprise strike. A character moving this fast would have 5 times as long to plan each move, and at close range their attacks would be basically unavoidable. It would be extremely difficult to fight a character this much faster without much better abilities and/or starting at significant range. 

However I do think there's two scenarios that suggest characters might be able to reasonably fight someone much faster proportionally than these.

The Cheetah Scenario:

Ten times faster than an average human, a full order of magnitude, at 30 meters per second are cheetahs, the fastest land animal. It's also the speed of the fastest fish, the Sailfish, and is typically about the speed of a car on the freeway. Let's imagine a scenario where a hunter has a gun that can presumably one-shot a cheetah. If it doesn't kill the cheetah with one-shot, it will basically take it out of a fight with one-shot. Conversely if the cheetah reaches the hunter it's similar that he will die or be rendered unable to fight almost instantly. 

Thing is, cheetah hunting is a thing and it's not considered especially dangerous compared to other forms of hunting. Granted, this is primarily because hunters use stealth and range, but there are accounts of people defeating cheetahs in close range, even before the creation of guns. Cheetahs don't just suddenly appear biting the neck of an enemy like an anime character. The reason for this is is acceleration. Cheetahs and indeed everything that rises to a certain speed doesn't do so instantly. Unfortunately there is no universal rate of acceleration but cheetahs take 3 seconds to reach top speed, and most biological organisms similarly take several seconds to reach top speed. Within 0.25 seconds, normal human reaction time, the character will only reach a fraction of their top speed. Now this obviously various alot not just between series but sometimes within the same series how long it takes a character to accelerate to their top speed, but assuming a somewhat naturalistic acceleration, characters might be able to react to another character whose top speed is several times what you would assume the character could react to just by comparing their top speeds so long as they react before they reach their top speed. Similar to man with gun vs cheetah, if a powerful telekinetic fought a speedster 10 times faster than him, I don't think it's an impossible scenario for the speedster to just lunge for the psychic and the telekinetic to react in time to telekinetically just throw the speedster backwards, and do this over and over again, especially if the speedster can't reach their hypothetically top speed before the telekinetic can react and throw them off again. This is where the method by a which a power is utilized comes into play and why thought based powers can be so dangerous compared to abilities requiring touch or hand motions.

The Fastball Scenario:

Professional Baseball Players are expected to semi-regularly hit fastballs moving anywhere from 95 mph to 105 mph (~42.5 to 47 meters per seconds), speeds over 14 to 15.66 times faster than an average human's speed. Even an "average" pitch for is 92 mph (~41.1 meters per second). This video depicts an "average man" learning to hit a fastball in two days and discusses the difficulties of hitting an object moving that fast. This scenario isn't identical to a fight. A character is a much larger target than a baseball, and can actually swerve and move around as they approach. However this seems to suggest to me that at a range of 20 meters or a bit less, especially for a character depicted as being highly skilled, reacting to a character moving a dozen times faster than them isn't impossible. Obviously these are still the difficulties of when they are in any kind of mid-range or close range, and landing a hit on them when proportionally the slower character would seem to be moving at the speed of a tortoise or a sloth, however the slower character can still sort of fight them and depending on what abilities they have, can potentially win even without just pure ability-stomping them. If they can teleport for instance they can teleport to a far range when the faster character tries to approach and because it doesn't require the slower character to hit, this may allow them to consistently avoid the slower character. If the character can release omnidirectional energy or lightning or fire, than while the slower character might be able to avoid it, it can keep them at bay if they try to approach. This is especially true through usage of "aim-dodging" or moving pre-emptively based on tracking an opponents intent. 

This suggests to me that how differences in speed would seem to the two characters:

1-3x: Any difference in speed is going to be some advantage obviously but this is roughly the range of normal humans to athletes and is a range that shouldn't be too difficult to overcome. A character with much more skill, but still completely human level of skill, should be able to overcome a speed gap this marginal. The bigger advantage is that the faster character will have find it easier to avoid their opponent's attacks since they will seem to be sluggish in comparison but it's not a dominating fight factor.

3-5x: This is where the speed gap starts really getting noticeable, comparable to humans and peak humans or low level superhumans. A character moving this fast an average human is going to find hard to even tag in the first place, and find it very difficult to tag in response. A dramatic disparity in power or skill can make it up, but this is where a speed gap will be pretty noticeable to both characters as the faster character could easily dip and dodge out of basically any melee range without getting hit, and their attacks at close range will be impossible to avoid.

5-15x: The general boundary of where a character can be expected to reasonably fight speed-wise. If a character is beyond this then either the slower characters abilities are so much stronger that it's a stomp for them, or alternatively the faster character is going to speedstomp. This is a somewhat possible fight particularly if the slower character has better abilities or abilities that are good especially for fighting quick characters; things like teleportation, general shields, large area of effect attacks, and thought-based powers. The slower character's attacks will seem to be moving in very slow motion to the faster character while the faster character's attacks will be essentially all baseball fastballs to the slower character.

Anything past this is pretty unreasonable, assuming you know the characters speeds exactly and they have human-proportionate reaction/acceleration speeds.

Disproportionate Reaction Times in fiction:

What about when a character has reaction speeds that are disproportionate to their movement speed.

In the vast majority of cases I don't think it makes sense for characters to have disproportionally slower reactions compared to their movement speeds, nor do I think that should just be assumed. I don't want to get fully into that because it could be its own blog but basically if a character had disproportionately slow reactions then when moving at top speed, everything around them would seem to be moving in the opposite directions at fast forwarded speed. 

The opposite however does clearly happen sometimes in fiction, that being cases where a character has disproportionally high reaction speeds. For these characters even when moving at top speeds, things seem to be moving in slow motion. In real life it doesn't seem like you can train your reactions to be that much faster than an average human's. The lowest estimate I saw when I looked was reaction to visual stimulus was 0.1 seconds, 2.5x faster than normal. I don't think that should be taken as a multiplier where it's like peak human skill type characters can react to thinks 2.5 times greater than what they otherwise would be able too, but I do think it provides a good general metric to assess. If a peak human skilled character fought a character that is 1.1 times faster then you think they could react to, skill can compensate. On the other hand it probably wouldn't be able to compensate for something 4x faster. 

If a character has reactions vastly higher than their movement speed, they usually, though not always have some way of using those reactions, either they have thought based powers, or they can move in very short bursts at their reaction speed, or they can move their hands that fast as well just not their whole body etc. If you imagine a character with lightspeed reactions/hand speed but normal human movement speed in general fighting a character with general lightspeed movement speed, the former would basically be unable to move, be frozen in time for their fight but could shoot beams or shield or what have you. The two could still realistically fight, it's just the slower character would be at the disadvantage of having irrelevant movement speed in comparison.

Speed Precision:

All of this has been assuming you know the characters exact speed measurements, but in reality the most contentious part of all this is what the characters actual values actually are. To me the thing that doesn't get acknowledged nearly enough in most vs debates for both speed and power is the inherent fuzziness of the numbers. Most calcs rely on estimates, especially lowballs, and a lot of characters are scaled just to being "somewhere in the range" of a number rather then specifically at it. Here's an actual example I recall having one.

Character A could kinda keep up though was slower than a character that had a casual feat of 60,000 times the speed of light.

Character B traveled from the Sol System to the Galactic Center during a 4 year time skip, calced at 7,000 times the speed of light all while fighting demonic forces the way there.

Do you just say Character A has a really big advantage for being 8 times faster? I wouldn't. Character A downscales from their feat, while Character B's feat is ludicrously lowballed. It sounds clear when laid out but I've seen people say that things as low as a three times differences were completely insurmountable, even when the slower character had a passive luck aura and had a super lowballed speed calc while the faster character had a speed calc that was not very lowballed. I think the solution to this part is to, when possible, try and compare the characters feats directly rather then simplifying to just numbers. It takes a bit more time and effort but I think it feels more naturalistic.

There's no real way to account for this part because it entirely on how fuzzy the two characters speeds are. 

So what level of speed gap can characters fight? It depends on what other abilities or skill level the characters have, whether their acceleration and reaction speed and how precisely you know the two characters speed. Roughly speaking if a character is well equipped towards fighting characters with a higher speed then than than while a speed gap is always an advantage, I think a gap of 5-10x is reasonable, maybe 10-30x if they have dramatically better abilities and they can keep stopping them before they can accelerate to top speed. If one character's speed is fuzzy and lowballed, you can maybe get a few times more, based on the reasonable range you could interpret their speed feat as being.