Ok, some of these have faced off individually on the forums, but i couldn't find a free for all version. They are all in character magically transported to a cubic mile arena filled with overgrown stone ruins for each round. Standard gear, but no outside help. Any and all in game/cutscene feats available, including sequels and DLC. Standard elimination techniques (no team-ups) and once their bodies are wrecked sufficiently, no ridiculous regeneration or transfer of consciousness. (ie. Mercer didn't "tank" the nuke, he barely survived by consuming and healing afterward. that kinda stuff.)
Round 0: No prior knowledge, pure fist fight.
Round 1: No prior knowledge, all abilities and gear.
Round 2: Good knowledge of each other's abilities and a full day to prep mentally.
Round 3: Assuming only their gameplay stats, who do you choose to play as to win the tournament? (just imagine a cross-over game like Super Smash Bros, but darker!!)
Bonus Round: If they all teamed up and got over their differences, what DC/Marvel/Image/Anime teams, armies, or individuals could they take on together for a good hard fight? (be specific with what versions, etc.)