A battle pass for fighting games, if you're a competitive player like me, is easily ignored because it's a carrot at the end of a stick to keep you playing to earn cosmetic items. In fighting games, this currently only exists in Street Fighter 6, Tekken 8, and kinda sorta in Mortal Kombat 1, to my knowledge.

A season pass is where you get new characters, just like you can get expansion content in any other game. These are what I do buy as a competitive player. They usually come with 4-6 characters that are released over the course of the year. There's no world where I wouldn't want to have every character, since even if I don't intend to play as that character, I'd still want to bring them into training mode to figure out how to beat them. So the package is slightly discounted compared to buying each character as they release, and I know that I'll have each character unlocked the second that they're available.