Let's say you watched the prequel trilogy with zero knowledge of the overall story of Star Wars and didn't even know who Darth Vader was. Would Anakin's turn to the dark side feel realistic to you? We can basically forget the first movie since it doesn't affect his character arc at all. In the second movie his mother dies but that's really the only tragedy in his life. Yes, he was a slave, but all that really amounted to was needing to work for Watto--his life really wasn't much different than the non-slaves, he just couldn't leave. Pod racing seemed like somethng he enjoyed. You'd think that if he were to become obsessed with keeping his loved ones from dying to the point that he'd be willing to betray the Jedi and murder children, he'd have had a lot more terrible things happen to him. There's also the question of "why didn't he ever return to Tatooine to free his mother from slavery in the years after becoming a Padawan?". So he goes from a normal, good-natured kid to full-on evil based on a single death of a loved one that he himself could have prevented if he'd bothered to.

I feel like if I just watched these movies alone, I'd come to the conclusion that Anakin is a psychopath not worthy of the redemption he eventually gets.