The Invasion angle no doubt, everything else listed in this thread (except of Blue Blazer) was just an idiotic storyline or a gimmick that could be fixed and even if not, it damaged only the career of one wrestler but the Invasion angle was about the future of pro wrestling in North America and we still feel the consequences. No misuse of Kane, guys like Cena & Reigns being forced down our throats and Trish Stratus acting like an animal can be compared to the golden opportunity they have missed.