Powers and Stats
Tier: 7-B. Likely 6-A via environmental destruction.
Origin: Avatar: The Last Airbender
Age: At least 100 million years old (Claims to have lived 10,000 lifetimes before humanity had even appeared [Note that one lifetime for Vaatu is 10,000 years])
Classification: Dark spirit, Spirit of chaos and darkness
Powers and Abilities: Superhuman Physical Characteristics, Immortality (Types 1, 3 and 8), Flight, Can extend his limbs/tentacles, Regeneration (Low-Godly as long as Raava exists), Energy Projection, Shapeshifting (Can increase his size by feeding on chaos and anarchy), Plant Manipulation, Can corrupt other spirits, Able to fuse with a human to create a dark Avatar
Attack Potency: City level (Nearly killed Wan, seriously damaged Korra in her Avatar State. Accidentally destroyed small mountains in his fight against Raava). Likely Continent level via environmental destruction at full power (He was going to cover the world in darkness and then reshape it, when he possessed Unalaq he nearly managed to do so)
Lifting Strength: Superhuman
Striking Strength: City Class
Durability: City level (Took a beating from Wan and he was fine, took a beating from Korra and he was fine, crashed against small mountains and he was fine). His regeneration and immortality make him very hard to defeat, the only known way to reliably "kill him" is to make him fuse with a human and killing said human when he/she reaches the Dark Avatar State.
Stamina: Nearly endless (Fought Raava for at least ten thousand years and was imprisoned inside the Tree of Time for ten thousand years)
Range: Hundreds of kilometers
Standard Equipment: None
Weaknesses: He can be temporarily killed if he is disintegrated, but he will revive, he probably can be killed if he fuses with a human and said human is killed in the Dark Avatar State.