Suggestions by @cartoonmultiverse

Ultron Infinite

as Ultron Infinite in Aang

Sage (High guardian spice)

as Sage in Aang

Moana (Disney Character)

as Moana in Aang

Glimmer

as Glimmer in Aang

Michelangelo (TMNT 2007)

as Mikey (07) in Aang

Kuvira (Legend of Korra)

as Kuvira in Aang

Lord Shen

as Lord Shen in Aang

Kang the Conqueror (Marvel Cinematic Universe)

as Kang the Conqueror in Aang

Catra

as Catra in Aang

He Who Remains (Marvel Cinematic Universe)

as He Who Remains in Aang

Twilight Sparkle

as Twilight Sparkle in Aang

Wolverine (Marvel Cinematic Universe)

as Logan/Wolverine in Aang

Iron Man (Marvel Cinematic Universe)

as Tony Stark/Iron Man in Aang

Miss Martian

as Megan Morse/Miss Martian in Aang

Zuko

as Zuko in Aang

Aang

as Aang in Aang

Raphael (TMNT 2007)

as Raph (07) in Aang

Donatello (Rise of the TMNT)

as Donnie (Rise) in Aang

Donatello (TMNT: Mutant Mayhem)

as Donnie (MM) in Aang

Leonardo (Rise of the TMNT)

as Leo (Rise) in Aang