I'd probably go with the Glenn Davis trade (shockingly, disgustingly bad) with the Heathcliff for Lowe/'tek trade coming in second, but two more recent ones come to mind as being really bad:
Erik Bedard for Adam Jones, Chris Tillman, and George Sherrill (as well as a couple other nobodies). This one is especially vexing because Johan Santana was on the trade market during the same offseason and the Mets gave up less than the Mariners to get him.
and, in a reversal of most of these trades:
Dontrelle Willis and Miguel Cabrera for Dallas Trahern, Burke Badenhop, Frankie De La Cruz, Cameron Maybin, Andrew Miller and Mike Rabelo. I actually had to copy/paste this because I didn't remember most of the names and probably never will. This is one of those trades where the team that got the established superstar was actually the big winner, and the team that got the prospects was completely and utterly fleeced.
Of course, Miller would go on to have some success as a reliever and Maybin would have the odd productive year here or there, but it doesn't even come close to Miggy's production and impact in Detroit.
The funny thing is that Willis ended up amounting to nothing in Detroit, but if he had been roughly 80-90% of the pitcher he was in Miami, this would have been even more lopsided.
