Gus Fring is dead. Long live Gus Fring!
A truly amazing season finale! I can't wait for the remaining seasons.
It is interesting to contrast the evolution of Walt and Jesse. Jesse originally came off as the badass drug dealer. However, the path that he has chosen (or, rather, that Walt has chosen for him) is taking its toll. Losing his girlfriend to a heroin overdose (which was fully preventable by Walt, let's not forget) nearly broke him. The scene in which he dialed her phone over and over just to hear her voice on the answering machine was heartbreaking. And then, having to kill Gayle seemed to push him over the edge - he develops a full-blown case of PTSD which still seems to haunt him.
Walt, on the other hand, started out as a mild-mannered schoolteacher, the kind who would literally not be able to hurt a fly. His first killing (in self-defense) was awkward and amateurish. But it didn't end there. By the end of the fourth season, he is an accomplished killer. Note how he kills Jesse's guard without even a second thought. It seems that the more his body count rises, the less remorse he feels.
Gus is now dead and gone (in a rather spectacular manner) - but it doesn't matter. For all intents and purposes, Walt has subsumed Gus and become the embodiment of ruthlessness, amorality and yes, true evil, that Gus possessed.
Here's hoping that Walt finds some measure of redemption, and regains his humanity before "Heisenberg" corrupts him forever.