The Dark Avatar refers to Unalaq after he merges with Vaatu during Book 2. It is not Amon, and it is not another name for Korra’s Avatar State.
The two pairings
Korra's Avatar identity is tied to Raava. In Book 2: Spirits, Unalaq merges with Vaatu, creating the opposing figure described as the Dark Avatar. The conflict takes place around Harmonic Convergence.
Understanding the pairings makes the finale easier to follow than treating “dark” as a generic label for any villain with powerful bending. Amon's abilities belong to the first book's bloodbending reveal, not this spiritual union.
What happens to the past lives?
The Book 2 conflict severs Korra's connection to the Avatars who came before her. That is not the same as saying she permanently ceases to be the Avatar or cannot use the Avatar State. The distinction matters when discussing the later books and the successor story.
Why the terms get mixed up
Short clips can show visually similar moments of heightened power while omitting the story around them. A glowing character is not enough to identify the mechanism. Check who is present, whether the scene involves Raava or Vaatu, and which book the episode belongs to.
Where to watch for context
Watch Book 2 in sequence, including its finale, rather than beginning with a battle montage. The Unalaq profile introduces the human side of the conflict. The cataclysm guide explains why these Book 2 events should not automatically be equated with the later ruined world.
Sources & further reading
Sources for the facts above. Commentary and practical advice are identified in the text.
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