what i love most about the character development in uno is the ways in which the characters stayed the same. remi has taken off her rose-colored glasses but she's still unendingly kind. blyke will fight any injustice he sees but he's still impulsive and a little reckless. isen has become so much braver but he's still practical and doesn't have a hero complex. arlo is finally (finally) willing to fight the institution and even in that he needs to appear perfectly level-headed and in control. john is at last doing something heroic - by fighting people, of course - and he still completely disregards his own wellbeing and his limits. seraphina is fully rebelling against everything her parents stand for and support, but now she cannot afford to make mistakes. she needs to train her ability back to its old level and perhaps even above it, she (and leilah and darren) needs to know as much as possible in order to stay ahead of the authorities and spectre, and she has no time for frivolous things like friendship.
all of this is to illustrate that well-written character development involves keeping some key traits at least somewhat intact, and adapting other existing traits into similar ones that best fit the new environment. time and trauma change people, of course, but in a lot of ways people will remain similar to who they once were, and writing your characters this way often makes for more dynamic and emotionally devastating character development. the 'what have you become?' moment often is a lot more impactful if there are still traces of who they once were present, and positive character development is often a lot more believable if the character doesn't completely change personalities.