6. Tara Little
Remember Tara Little (Brooke Nevin)? She was part of the 51 team during the show's first season, and while she seemed like a straight shooter at first, it didn't take long for her manipulative tendencies to surface. She accused Severide of misconduct, which forced the firefighter to clear his name.
Eventually, Little came clean and admitted that she falsely accused Severide as a way to further her career as a medic, but by then, her credibility had been shot, and she could no longer be trusted by the rest of the 51.
Once again, Little didn't jeopardize any lives, but the fact that she nearly ruined a career is enough to get her a spot on this dubious list.