Deathstroke vs Capt. America vs Batman
These three have stalemated each other over and over, the only reason one or the other EVER wins is because of a plot hole.
Everyone gets their usual weapons, and they all get 1 day prep.
No ring out, no K.O...you either die or don't.
Only one will survive.
They are thrust into a unfamiliar setting with high winds and maybe some pissed of wolves...and a polar bear ( to keep anyone from running off to make more plans).
If they want, they can double team another, to take the best out first.
I'd prefer this not to happen because I'd like to see a clear winner.
They're all fighting for what motivates them the most.