The best transition from antagonist to hero

I suggest Stathis Borans from The Fly (1986). He is the least-developed of the main characters, and rightly so as the relationship between Seth and Veronica drive the plot, but what we do know about his character is mostly negative: he stalks her, makes a scene in public about her relationship with Seth, breaks into her apartment to ambush her when she gets home, and suggests that they have sex despite her clear disinterest in him. He’s a creep.

And yet, when Veronica has no one to turn to, Stathis is the one who pulls some strings with a doctor that he knows to get him to see her in the middle of the night. And after Seth kidnaps her from the doctor’s office, Stathis goes to Seth’s lab with a gun to rescue her, losing a hand and foot in the process.

It’s not a long movie but it’s so brilliantly written that we are solidly against him when the story needs us to be against him and solidly sympathetic and appreciative of him when he plays the hero. In a lesser movie this would feel like whiplash, but not in The Fly.