My favorite by far is Starlight Glimmer! I love how real she feels in terms of making mistakes and dealing with social anxiety and the like. I also love how she is not only a character who was a former villain who became redeemed, but that this redemption also did not come from some magical and instant change in her character. It was through persuasion and realizing what she was doing was wrong, and endeavoring to change for the better. The main thing I would've wished to be different is that there'd be more starlight in season 6 specifically, as that contains some of my favorite episodes with starlight and it would've been interesting to see more of the dynamic of starlight being a pupil under twilight.