There is only one change that brings the climax of one of the films to a screeching halt. Vader boarding his star destroyer in ESB is therefore, hands down, without a doubt, the absolute worst SE change.

Jedi Rocks is the most embarrassing moment in any SW film but as a friend pointed out to me recently when we were discussing SE changes it is easily skippable (as is much of that portion of the film, sadly). Same goes for the Jabba scene in ANH. Still, terrible changes.

The color changes are pretty gnarly though I’m not sure I’d really classify that as a “change.” More like a colossal fuckup.