From the sounds of it, Flash seems like the best idea if you're going for pure survival. I don't follow comic books, but it sounds like Batman has "contingencies" for taking out people if they go rogue? I don't think he has a contingency if a magic person is going to instantaneously pop some random into another time period.
On the other hand, if I have nine super
heroes coming to kill me, I must be into some seriously heinous shit. In that case, sign me up with Iron Man because it seems like it would be pretty trivial to convince him to give me some stupid overpowered suit. At least that puts me on a power level within reason of these other characters to try and finish doing whatever heinous shit I've planned that would warrant cross-company franchises to band together to take me out.
At the very least I could lay claim to being one of a very select few to fight both Batman and Superman. I'd be immortalized forever in nerd discussions of "what if" scenarios.
Batman of course.
Nobody can beat that plot armor.
I mean, Batman can keep his plot armour and not die to the other nine while still suffering a climatic "loss" by losing the charge he was sworn to protect.
It's not like people close to Batman don't die constantly. I feel he's one of the worst options.