[DaneMcCloud]

Originally Posted by Dagnabit

There's a theory floating about that Vader doesn't fully embrace the dark side until after the destruction of the Death Star. Once Tarkin and the Moffs are gone, there's not much to keep him in-check.
He never really left the military or stopped fighting a war. He was a soldier for most of his adult life, and had that mentality And once the command structure was obliterated and a few "fellow soldiers" he admired were vaporized, he really let the hate start to flow.
Compare his demeanor between IV and V.

Interesting, thanks!