Mutants stom... No wait, movie mutants? Then most of them die, unless Xavier in Cerebro mind-kills Manhattan, with him being existentially conflicted and all. Also I don't remember much telepaths in Watchmen, so there's no reason for Manhattan to have resists for tp, meaning Xavier in a stomp.
Yeah... Flash would probably beat up Touma even without superpowers, given that Touma is a teenager, and Wally is thirty-something trained by Batman... Unless of course light novel feats, where his arm is Lucifer or something... But I digress.
I'm not sure In Thor and Hulk vs Saitama though. I haven't read the manga for some time now, and I remember there was time in strips when Saitama actually met his match, so... World Breaker Hulk would probably be able to take him on.
It's always frustrating to fight Index characters, since they're designed to be untouchable for anything except Touma =__=
Personally I join the opinion that Speed Force dump would probably work in first two cases. Or, since battlefield isn't defined, we can assume he runs to Fortress of Solitude, borrows Phantom Zone projector and dumps Accelerator there.
Assuming Kyle wouldn't die from the overload and had complete mastery over all rings, how could he lose?
Well, for example the rings grant him complete control over Emotional Spectrum, which is rather nice - hard light constructs, bonus powers of individual lights, and (arguably) the White Light of Life.
Thanos on the other hand, no pun intended, controls reality with just 1 (one) Infinity Gem. An argument can be made that he can wipe out the Emotional Spectrum completely with only Mind or Soul gems. And Infinity Gauntlet houses what, six of them? So yeah, this is probably a mismatch.