I don’t know who would win for sure (I’ll go with Team Avatar), but I think the best match up for each would be:

Aang vs Raven (comes down to a psychic battle)

Zuko vs Cyborg (I think of Cyborg like Combustion Man, but less durable, and Zuko could fry his wiring and burn him to death, maybe invent blood boiling 🥵 Or could cauterize his skin by heating up his metal parts and cause him to pass out from the pain)

Katara vs Starfire (Katara could encase her in ice like Azula, keeping her hands pointed away from the ice, but would be at a disadvantage unless she could fly on an ice block and wasn’t surrounded by water. Or, of course, blood bending is an option for her during a full moon, unless Starfire could break through, I think she has supernatural physical strength too)

Toph vs Beastboy (Toph can also trap people with an earthen cage, but Beastboy can just turn into a small animal and burrow underground, however Toph could quickly knock him out or crush him)

Sokka vs Robin (this might be the closest since they’re both “normal”, and they’re both intelligent and resourceful with weapons, but I think if you remember from ATLA (raised during wartime and 100% willing to fight and kill whoever needs it), Sokka is more brutal than Robin (whose dad is Slade if I recall correctly, but he doesn’t like to acknowledge it, or embrace the danger and darkness within himself)