How they Compare: Eris (Saint Seiya)

Of all the deities opposing the Good Goddess Athena governing human wisdom and civilization, none are said to be as malevolent as spiteful and sadistic Eris, the Goddess of Chaos and Discord. In her disdain for Athena she has come to threaten humanity on multiple occasions. 

Eris as a Saint Seiya Goddess is very powerful! 

Eris is the abstraction of discord, and so long as strife and conflict exist, she can reappear any number of times. Chaos is her natural domain. It is noted that with her apple of discord she can cause discord and strife amount people. 

Her sheer power was so great that even in a weakened state she was able to put up a fight against Gold Saint Scorpio Milo and when she was sealed away by Athena at the edge of the universe, she was able to call evil souls to her from across the universe to strength and free her. 

She is likely at least as strong as her brothers Thanatos and Hypnos who were so powerful that they were able to casually defeat the 5 Hades Arc Bronze Saints, and was strong enough to resurrect the evil half of Gemini Saga and strengthen him further, and he still serves her. This is rather notable as Gemini Saga's attack power with the Galaxian Explosion was so great as to be superior to the Starlight Extinction of Aries Mu which destroyed the universe of the Titan Iapetus. 

Indeed given their fight it seems Eris is nearly as strong as the Goddess Athena herself. Athena was able to fight with limited success the Heavenly Emperor Hades who was able to casually maintain 3 universe sized dimensions with his divine cosmo. 

In addition Eris should easily be as fast or faster as Capricorn Shura with the power of miracles, when he exceeded the initial inflation speed of the Big Bang requiring speeds of dozens of septillions of times the speed of light. 

Though beyond sheer power, Eris has many other advantages. 

As a Goddess Eris has control over the 6th, 7th, 8th, and 9th senses. The 6th sense known as mind is properly sapience but also when mastered gives abilities like telepathy, aura reading, teleportation, telekinesis, pre-cognition, astral projection and so forth. The 7th Sense grants the ability to perform miracles, acts which warp reality as well can replace any of the lower senses should they be disabled. The 8th sense grants control over life and death, such that one can live and maintain one's senses in the Underworld and can come back to life at will. Finally the 9th sense grants godhood, including powers like immortality and abstract existence.

In addition to all these Eris has more powers. She has incredible soul manipulation, able to call evil souls to her while sealed at the edge of the universe. She has the ability to destroy or manipulate matter and energy down to the atomic scale. As a Goddess, any non-divine attack launched at her will be reflected upon the user, and her presence passively disables the lower 6 senses. 

Eris also has control over creation and destruction. She can at will create her dryads, her servants, or create bodies for disembodied souls and can also destroy opponents, erasing them from existence including on the astral plane.

She also has resistance to a large variety of abilities including time manipulation on a universal scale, atomic scale matter-energy manipulation, colds somehow even lower then absolute zero.

And with all that it is said that Eris' greatest strength is her cunning and manipulative nature. She is very good at sowing discord and discontent. 

So how much discord could she cause in other universes.

In Marvel Comics, Eris would be roughly on par with a Cosmic Cube Level Entities. While her maximum power might be slightly higher then theirs, she would be very similar and have similar levels of versatility. Her abstract nature would also make her very difficult to defeat. Using her stronger abilities she might be able to beat a Celestial Level Entity one on one, though such is more speculative.

In DC Comics Eris would be a massive threat to the Earth, even Pre-Crisis or Rebirth, and not even major powerhouses like Hal Jordan or Doctor Fate would be likely to beat her one on one, though it is possible. Especially if she is subtle in her approach it would be very difficult to beat her, though if she is uncovered an assault by a large number of forces similar to her would probably defeat her.

In the Digimon multiverse, Eris would be similarly a large threat but not a potential verse-soloer. She would be very similar both in powerset and power level to one of the Seven Digital Demon Lords which can rapidly destroy Zones the size of universes. While that would be very strong, there would be still a number of high tier Digimon stronger then her.

In the Pokemon Multiverse, Eris would be near the top, and be able to defeat any of the 3; Palkia, Dialgia or Giratina in a one on one fight, however it would be difficult for her to defeat multiple at once and she still would likely not defeat Arceus in a direct fight.

In the Serial Experiments Lain Universe, Eris would be potentially able to solo, as she would be comparable in a fight to Lain herself, who by the end is the top tier. Though Eris would have vast difficult trying to actually effect or hurt Lain, the same would be true in reverse and the two would potentially stalemate for a long time.

I actually don't know much about the Grim Adventures of Billy and Mandy verse, but I was informed by someone who was knowledgeable on it then it's version of Eris would be comparable to the Saint Seiya Eris, which was surprising.