The Collector (The Collector)

The Collector is the titular character and antagonist of the 2009 horror film The Collector and its 2012 sequel The Collection, and he is one of the most sadistic and perverted villains in cinema, even by horror standards, willing to murder and "collect" hundreds (maybe thousands) of people to satisfy his sickening urges. He always wears a mask to hide his identity.

History
The man who would become The Collector was the son of a museum owner and entomologist. One day, the father went insane (possibly due to chemical exposure, though the exact cause is unknown) and killed his family, stuffed them, and then placed them at the table on Thanksgiving and ate with them as though they were still alive. Only his son survived, but the experience warped his mind.

Later on in life, The Collector would himself become a licensed entomologist and presumably led a legitimate life, but underneath this was a perverted murder and kidnapping operation, in which the man, called The Collector by the authorities and his victims, would target whole families and kill all but one member, who would have the misfortune of becoming a part of his "collection", and would either be killed through gruesome experiments (after which his/her body parts and bones would be reassembled to look like insects) or driven completely insane. The collection was kept at an abandoned hotel, which was rigged with traps to kill off any would-be escapees and intruders.

The Collector (2009 film)
In the first film, The Collector targets an old couple, killing one while stuffing the other in a red trunk and adding him/her to his collection. Later, he targets the Chase family, posing as a bug exterminator to gain access to their house. When he begins his assault, he brutally kills all but one of the family members through various traps he had set up around the house. He is stopped from killing (or presumably collecting) the last member, Hannah, by ex-convict Arkin O'Brien, who lures the fiendish man into one of his own traps before escaping the house with Hannah. Unfortunately, The Collector seemingly has the last laugh, as he survives, kidnaps Arkin as he was being driven to a hospital, and adds him to his collection.

The Collection (2012 film)
In the sequel, The Collector kidnaps Elena Peters, the daughter of a wealthy socialite, after she escapes one of his rampages and rescues Arkin by sheer chance. During this time, he also kills a large number of teenagers by either shredding with rotating blades, impaling them with swords, and squishing them with a falling ceiling. Elena's bodyguard, Lucello, forces Arkin to lead a team of mercenaries into the hotel where The Collector keeps him victims to rescue Elena in exchange for terminating his criminal record. The mecenaries are killed or captured one by one, while Elena manages to escape the trunk she'd been stuffed in on her own and tries to find an exit, while Arkin separates himself from the group in an attempt to find a way out. Eventually, only Arkin, Lucello, and Elena are still alive.

The Collector tries to burn down the building, but he is stabbed repeatedly by Lucello before killing him, and is then thrown down a laundry shoot and set on fire by Arkin before the latter escapes with Elena. After the fire is put out, the police inform Arkin that no body was found, and he fins The Collector's charred mask in a trunk. Sometime later, Arkin tracks down The Collector to his house and threatens him at gunpoint. The Collector faces him (though the audience still can't see his face) and ask "You here to kill me?", to which Arkin responds that he is going to put The Collector through the same tortures he subjected Arkin to before killing him. The Collector tries to attack Arkin, but Arkin knocks him into his own red trunk and repeatedly slams the lid on his fingers (screaming "Fuck you!") before sealing him inside.

Arkin presumably made good on his promise before killing The Collector.