I have been adviced to take a look at characters I already know that are in films that portray the same characteristics of who my Loki is. Loki is an evil genious that has been chained up so he doesn't cause harm so basically I see a locked up convict, mass murderer and an enchained psycho. What comes to mind is two characters in Simon West's 1997 film "Con Air". The two characters in mind are John Malkovich's Cyrus (the Virus) and Steve Buscemi's Garland Greene.
John Malkovich's Cryus the Virus: