I’ve written before that all things considered; Phillippe Aumont might be the worst Phillie ever. There were other players who had brief, awful stints with the Phillies, and some who put up fewer wins above replacement. But factoring in how they acquired him, and how sharply his star declined, I think Aumont has a definite claim for being the absolute worst.
You likely remember the story: When the Phillies couldn’t come to an agreement on an extension for Cliff Lee after the 2009 season, they quickly pivoted to trading for Roy Halladay. Because ownership didn’t want fans to get excited about the prospect of having both Halladay and Lee in their rotation, they simultaneously traded Lee to the Mariners.