So that might be useful in the scenario you're writing -- either by showing that he is still like that in some ways, or by putting him in a situation that previously would've led to violence and showing that he's changed by having him back down and turn away from it.

This is useful advice, thank you! I am trying to show the character struggling to change, but sometimes I worry the change is taking place automatically. I really appreciate your perspective!

You can put your character in a situation very similar to something they encountered in canon, and have them make a different choice, while at the same time recognizing that the "old" them would've done the other thing.

This is a good tip, and now I'm going to go back through what I have of the story and see where I can use it!