Accelerator is the strongest Esper in Index. He can manipulate vectors in a way that works like Graviton’s barriers. You can’t hope to stop him with direct attacks since they will just be bounced back. The best way to stop him is a bunch of sneak attacks or to just overwhelm the guy. After all, a single good hit will take him out if you get past that since he’s no more durable than your average teenager but that’s a lot harder than it sounds. Ms. Marvel does have a lot of power up her sleeve but I think she won’t quite have the speed to pull this off. Accelerator wins.