Probably not quite what you wanted, but P=NP. When you look at what does that imply then it's hard to think that it holds. Scott Aaronson has a checklist on ho

Probably not quite what you wanted, but P=NP. When you look at what does that imply then it's hard to think that it holds. Scott Aaronson has a checklist on how to quicky reject a P?=NP paper, and one of the best methods is to check whether the paper proves something weaker first.