I always thought edge's spear looked lame; the move was over-done way before he tried his hand at it, and Edge is just not big enough to make it convincing. He should go back to the Implant DDT
FU and STFU both suck, but as long as Cena doesn't try to come up with another finisher, I'm okay leaving it at that. The protoplex looks alright, I guess.
I think it's funny people attacking Mark Henry's slam, it's just about the only half-decent looking thing he does in the ring. If Mark Henry attempted a powerbomb on somebody, I think he'd probably kill them.
The GTS looks bad because Punk's got little knobby knees and the guy only drops like a foot before the knee connects. Not a lot of impact, and when the impact is right, someone breaks their face.
I love Christian, but I never could figure out why he doesn't just use the diving inverted DDT as a finisher, it's simpler, could be pulled off instantly like the RKO, and looks a lot more devastating.
But to answer the question, finisher that doesn't fit the wrestler: gotta say either Edge's Spear, Big Show's KO punch, or Cena's STFU, so maybe that gives you an idea of which match at WM25 is probably gonna be the worst.
A 7 foot giant doing a punch as a finisher though? I don't know how you could beat that. Show should be Vader bombing people.