59. Superboy Prime vs. Supermen
As established in a previous fight on the countdown, Conner Kent managed to defeat the plans of Alex Luthor and Superboy Prime in Infinite Crisis #6.
Well, while that basically took Luthor out of play, it did not take Superboy Prime out of the picture, and in Infinite Crisis #7 (by Geoff Johns and a bunch of artists, including Phil Jimenez and George Perez), Superboy Prime decides he is just going to destroy Oa, which is the center of the universe, in a fit of rage (sort of a “If I can’t have my perfect universe, no one can have a universe!”).
A whole pile of the Green Lantern Corps show up to try to slow him down, but they are mostly unsuccessful (and about three dozen of them lose their lives in the process) but we soon learn that this is part of a risky gambit.
The other two Supermen, Kal-L (Earth-2 Superman) and Kal-El (the “main” Superman), show up and drag Superboy Prime through the place where Krypton once was (essentially now a field of kryptonite) and they then go through the red sun of Krypton. The three land on a nearby planet (the Green Lantern Mogo) where the three are now all powerless.
Then it comes down to a good ol’ fashioned fist fight, with Kal-El finally being able to put the kibosh on Superboy Prime, but not before Kal-L dies from injuries sustained during the fight.