15. Brian McCann, 2013: Five Years, $85 Million
Probably the ghastliest deal on this list, if not for that other, slightly more ghastly deal ... and that other one that's also worse ... yeah, the Yankees have full-scale beefed it a couple times recently, haven't they?
McCann was supposed to be the Captain of the Unwritten Rules of the Yankees' mid-2010s spending spree, and though he ripped 20 homers per season in the Bronx and somehow finished 24th in the MVP voting in 2015 (26 bombs, 94 RBI, .232 average), he was well below his peak, ranking as a league-average offensive player the entire time.
Anecdotally, he also had a propensity for popups to the right side of the infield. The McCann experience was no fun -- just the way he likes it.
Naturally, he ended up on the 2017 Astros and delivered some big blows at the tail end of the ALCS. Why wouldn't he have done that? Had to see that coming. Just like McCann's teammates.