How did you tolerate or deal with someone else at work who daily complained about everyone, their job, the command team and was disgruntled?

Some of us may have had another co-worker who always complained about the training, leaders, their job duties and responsibilities and so forth. It got to the point where no one wanted to associate themselves with this individual due to the negative influence and attitude. No matter what you did or said, the individual was never wrong nor would they change their outlook on anything?