Gaara vs Team Avatar Season 1 and 2

R1: EoS Gaara vs Aang, Katara, Toph, Zuko, Azula, Bumi, Ozai and Iroh (EoS for all. Ozai has bending)

R2: EoS Gaara vs Korra, Mako, Bo Lin, Tenzen, Kuvira, Zaheer, Lin and Suyin Bei Fong (EoS for all)

All are in character (villains are working with heroes against common threat).

Battlefield is the valley where Aang fought Ozai.

BONUS ROUND:

Both teams combine to fight Gaara, but the battlefield is an endless desert and Gaara receives Shukaku. Avatar team gets Kuvira's mech.

R1: Gaara stomps

R2: Not sure. Never watched Korra but I doubt any of them have anything on EoS Gaara.

Bonus round: An unholy stomp in Gaara's favor.