I actually love these achievements, such a plethora of references to the games and comics. Some are more obvious than others, tho
Fate of the Satsui no Hadou - Akuma vs Ryu
Raccoon City Incident - Chris vs Wesker (Maybe Jill can be thrown in here?)
Avengers Assemble - Cap, Iron-Man, Hulk because it says "the Big 3" but if you can do more it could also include Thor and She-Hulk
Female Flyers - Storm, Morrigan, Trish, and likely Phoenix
Whose Side Are You On? - Iron-Man vs Cap, or if it means teams, a Pro-Reg team (Iron-Man, Thor, She-Hulk, Deadpool) and an Anti-Reg team (Captain America, Storm, Spider-Man, Wolverine), as well as others not announced yet
Weapon X - Wolverine, Deadpool, and X-23
Darkstalkers - Morrigan, Felicia, and Lei-Lei
Duty and Deus Ex Machina - Captain America vs MODOK
Some of the more confusing ones:
Badds to the Bone - Does this mean changing an appendage like Spencer or adding in something like Wolverine, or is it more open to people like Captain America, She-Hulk, Hulk, Wesker, etc.
Copy This - At first I thought this was for Taskmaster for obvious reasons, but then I noticed the Mars and Venus symbols. Wolverine vs X-23? She-Hulk vs Hulk? And of course "Put an end to this game of spider and fly" implies Spider-Man, maybe Spider-Man vs Spider-Woman? EDIT: I think I get it now; Deadpool vs Taskmaster. Taskmaster traps people like spiders in a web and Deadpool is the fly, both have said this, and Taskmaster literally cannot copy Deadpool, hence "copy this!" Not to mention the rivalry between the two
I have to say, unlike SSF IV or something, I want to go and complete these.