I've watched Avatar before, but I think it's a pretty bad pick. Avatar is based around a four color-element world. Fire, Wind, Water, and earth. Which doesn't neatly fit onto the color pie, white/blue are usually the wind elements, but the water tribes aren't that Blue in their ideology, mostly Red/White with some Green so it feels off flavor wise. Fire slots into red pretty well and since their villains they'll probably get black, even if the faction on a whole is probably Mardu. Black and green both share a lot of the earth theming, and there's earth bending secret police ana apparently some evil earthbenders in korra, that I didn't watch, so I guess they'd get black due to being villains.
I saw some of the spoilers and Aang getting a mono-white card feels off. He's way more red. While Zuko as the fire lord gets Black, somehow, despite him not being Black in personality or powers. He's just black due to being the 'leader' of a villain faction. Even though the war has ended by that point. This even comes up with some other characters like Hei Bai who's very mono-green, maybe black/green. But gets a black/white card due to being a panda.
It's still a better fit than the two color good versus evil world of spiderman and marvel which lazily slapped black onto the villains even if it didn't fit power or lorewise.
Either way I won't be buying.