The newest feature of Pinto's Day-by-Day Database is team record by player appearance. In essence, you can see the Marlins' record in games in which [insert your desired player here] appeared.
Up at the top of the list, at least for guys with any significant number of appearances, is logical leader Robb Nen. After all, if Nen came in, odds are the game was looking good for the Fish. In terms of position players with 100+ appearances, Pudge makes his case for best free agent signing in franchise history. And starters with 100+ appearances are led by the 6.45 Million Dollar Man, Dontrelle.
But of course you probably could have guessed those three. What you probably didn't know is that twenty players can say that the Marlins failed to win a single game in which they appeared. None of those players can say they appeared in more games than Archie Corbin. The Fish were 0-17 in games in which he pitched. In that span, he racked up a 7.29 ERA. To be fair, only twice did he enter a game that the Fish weren't already losing; to be equally fair, he did give up the losing runs in one of those two games.
Technically Oscar Henriquez has a claim to the infamous title, as he nearly equalled Corbin's appearances (15) and pitched even worse (8.55 ERA). But since Henriquez never directly caused one of those losses, I feel it's only right to give Corbin the distinction.
If you're feeling brave, you can relive each of Corbin's fruitless games with Baseball Reference's Play Index.