The Superboy Prime retcon punch from the Infinite Crisis mini-series. You hadda be there. Or you at least had to hear about it. It's widely regarded as one of the most thoughtless, poorly concieved retcons in all of comics and it stands right beside a certain Spider-Man story that will not be named. Sometimes the things that comes out of an EIC's head frighten me.
Still, my disdain for THAT Spider-Man story aside, this image is pretty hilarious.