7. Keith Bamford
Keith Bamford (Chris McKenna) had a brief stint at the 51 during season 11, as he was tasked with being Severide's replacement. He was no Severide, to put it mildly. The character just didn't click in any capacity with the rest of the team, and whenever he tried to contribute, the results were painfully awkward.
The cherry on top, of course, was when Bamford made a joke about Cindy (Robyn Coffin), the wife of Christopher Herrmann (David Eigenberg). Cindy was battling cancer at the time, and the poor taste of his comment could have be overstated.
In truth, the only real joy that Bamford brought to the show was the scene in which he was let go.