No prep. To the death. For this scenario Thanos isn't immune to death and thusly can be killed. Pre 52 DC characters.
1. Magneto, Black Bolt, Captain Atom
2. Thor, WW Hulk, Hercules
3. Superman, Sentry, Gladiator
4. Apocalypse, Maxima, Martian Manhunter
5. Hank Henshaw, Alan Scott, Atrocitus
6. Dr. Strange, Dr. Fate, Circe
7. Darkseid and Odin (for this match only strength, speed and durability are used, which means NO MAGIC, SHIELDS OMEGA BEAMS, ETC)