@All_StarSupes: So in JLA he dumbed down, that mean, he ain't able to kill vegeta while he is a team member, by this logic(too)... I could write more why doesn't has flash chamce, but this isn't that battle. Vegeta would beat despero and JLA too.
Flash being dumbed down is called PIS, and PIS isn't used in battles. Flash would slaughter Vegeta, you can post the fight on any site and you will see 99% of people will vote for Flash.