Gus Fring (Season 4, Episode 10: "Face Off")
The kill that launched a thousand GIFs. As Walt's ice-cold antagonist since the middle of Season Two, Gus Fring needed a fittingly spectacular send-off, and that's what he got. At the culmination of an elaborate plot that required winning back his estranged partner Jesse's sympathies (by poisoning his girlfriend's kid) and enlisting the aid of his old enemy Hector Salamanca, Walt succeeded in taking down a kingpin with an improvised explosive rigged to a wheelchair in a nursing home. Like the proverbial chicken with its head cut off, the Chicken Man kept on strutting for a minute – just long enough to show the audience that half his face had been blown off in the explosion before collapsing. But the blast's most lasting fallout may well have been Walt's chilling proclamation after the fact, indicating he's now every bit as much of a monster as Gus ever was: "I won."