Gein is a malfunctioning hologram and the secondary antagonist of the storyarc "What Lies Beneath" in the video-game Star Trek Online, although technically without gender due to being an artificial intelligence Gein is refered to as a male for the sake of simplicity.
Gein was once a fully functioning hologram and likely helped out with the maintence of the space station until the Devidians invaded, causing a disruption in his program that caused him to manifest severe abnormalities akin to homicidal insanity in organic life-forms.
Stalking the confines of the former station Gein toyed with his victims, singing a strange and haunting song as well as cackling madly - ruthlessly killing any who got in his path: soon it would be only Gein and the Devidians left as the aliens did not attack Gein due to him being an artificial intelligence and Gein most likely ignoring the Devidians due to their otherworldly nature.
When a crew of Starfleet officers arrived to investigate the Devidian invasion they became the targets of Gein, who began to stalk them and attempted to kill them several times - at first toying with them as he had his other victims but showing aggressive paranoia near the end when he realized they posed a threat.
Ultimately Gein was defeated when the Starfleet officer shut down the corrupt program, it is uncertain whether or not Gein was ever repaired but considering the gruesome murders the rogue A.I. committed it is unlikely the Federation would risk such a move and Gein can thus effectively be considered "destroyed" (though never truly killed, as all A.I. are effectively immortal by their very nature).