Chris started the debate, and allowed Flash to set the stipulations. Chris took Superman. Flash could pick anyone he could think of, except DC comic characters. Flash chose himself. After a long guffaw from Chris and Mike, Flash set the conditions.
Few matches against Superman would ever be gladiatorial. Due to Superman’s power level. Flash constrained the battlefield to provide the opportunity to win this theorictical bout.
1. Standard city environment.
2. Average day.
3. Superman and Flash will not strike an accord to end the battle. (One has to kill the other.)
4. Natural weaknesses in effect.
5. Superman and Flash must have a physical confrontation of at least one blow. (No heat vision from orbit, or flying down from space to turn Flash into a pink mist)
Flash sees superman in the sky. He jumps from a tall building. He screams for Superman to save him. Superman swoops down and saves Flash. Once they are safely on the ground. Flash thanks him and gives him a bro-hug.* While close, Flash instantly grows a kryptonite beard and metal spiked hair. He drives his hair into superman’s skull, killing him instantly. Flash stands victorious.
*Bro-hugs with a slap on the back satisfy the 5th stipulation.