MM, Captain Atom, and Orion are the only ones who can stay in the fight, but I think SS would take out Cap fairly easily (if a relatively inexperienced Firestorm could, I think SS could easily). Orion is a powerhouse but could be overwhelmed by Glads and Nova combined. Everyone else gets 1-shotted.
MM would be incredibly tough to put down, but he's outclassed by the combined power of most of these guys...by a long shot.
@Nightflash: Wasn't the result Cap getting dispersed across the multiverse or something? (I dropped Firestorm after issue 4 or something and have been relying on other viners for info since...i could be wrong, so please inform me)
@Equonox: Issue 15 is the only firestorm issue I have and I only bought it because of captain atom. Firestrom was being controlled and forced to go all out and try to kill captain atom. He shot powerfull energy blasts and though he won but to his suprise CA was unharmed and was about to kill him untill the guy lost controll of firestrom. Something happened to CA and he flew away but not because of firestrorm. I think thats whats happened.