No. 1 - Seahawks trade for Percy Harvin, give up multiple picks (2013)
If Seattle had known more about Percy Harvin the person, maybe they wouldn't have done this trade. Oh, heck. Who am I kidding? Head coach Pete Carroll thinks he can help fix anyone, and that's a good trait to have. Unfortunately, Harvin was terrible in the locker room with Seattle and it is a minor miracle he didn't tear the locker room apart.
In fact, had Harvin ended up with a team that didn't have players like Bobby Wagner and Kam Chancellor, he might have. It is a testament to just how talented the Seahawks were in terms of physical talent and leadership that they were able to withstand Harvin. He was a player that had tons of athletic ability, but he just didn't seem to care about committing himself to be a good football player.
Harvin was a bit like the football player in the movie Summer School in that he shows up for one game during the season, disappears again until the Super Bowl and makes a splash by running a kickoff back, and leaves people wondering, "Where has this guy been?" Only to find out that Harvin was getting into physical altercations with other Seahawks, such as Doug Baldwin and Golden Tate.
So before Harvin was doing his best to win the jerk of the year award, the Seahawks had traded their first-round pick in 2013, along with a seventh-rounder the same year, and a third-rounder in 2014. That is far too much to give up for a guy who was an excellent return guy before he came to Seattle but was just slightly better than average receiver. Seattle traded Harvin midway through the 2014 season simply because he was just too much hassle.