The Anakin I imagined was someone who devoted himself wholeheartedly to justice. In many ways, he was even more proactive and idealistic than Luke, who often seems to be carried along by circumstances rather than driving them. But because his moral compass was set just slightly wrong from the beginning, he was drawn inexorably toward tragedy. To me, that is the kind of man who naturally becomes the Vader we meet on Endor.
So what kind of person falls to the Dark Side? Yoda tells us repeatedly in ESB. It is someone consumed by fear, anger, and aggression, someone who chooses the quick and easy path.
The Prequels emphasize fear and anger as the gateway. But looking at the world around me, I’ve often found that people who are consumed by anger and fear were not especially sincere to begin with. By contrast, when a genuinely sincere person ends up committing injustice or even terrible crimes, I think the traits of the Dark Side emerge in a different sequence.
First, they begin choosing the quick and easy path. This choice is not necessarily driven by selfishness or malice. Quite the opposite: they convince themselves that it is the most effective way to accomplish something good. Yet every shortcut they take gradually erodes the very ideals that motivated them in the first place. Only after that do anger, fear, and hatred begin to take hold. To me, this progression has always felt like the most believable way for a fundamentally good person to drift, almost without realizing it, into corruption.
At the risk of sounding self-promotional, that philosophy became the foundation of my own rewrite of the Prequel Trilogy, which I recently completed.
1000% this.