Played By: Jack Gleeson
There isn't a shortage of candidates for all-time great villains on Game of Thrones so far, but Joffrey's tempestuous temperament and bratty behavior put him over the top.
All of the show's characters will plunge knives (be it literal or metaphorical) into someone's back at one point or another in the series, but while most rationalize their tactics in the name of gaining power, Joffrey revels in cruelty for cruelty's sake. Series creators David Benioff and D.B. Weiss recently confessed that they sometimes worry about actor Gleeson's safety—they're afraid some overzealous fan might take a swing at him, drunkenly conflating him with his character.
If there's higher praise for a villainous performance, we don't know what it is.