He is portrayed by William Fichtner.
Mahone is an intelligent FBI agent who is troubled by drug addiction and a few skeletons in the closet that have alienated him from his family. He spends his time, working to atone from all the deaths and pain he caused from working with the Company, pairing up with Whistler to take it down. It was revealed that Mahone was forced by the company to become the corrupt cop, after his stress snaps and he kills Shales, the monster he had been hunting for years.
While his major attribute is being extremely intelligent, Mahone is an formidable fighter. He bests the similarly skilled fighter Lincoln and can effortlessly plow through many opponents if necessary.