As a show adds a few seasons to its roster, characters evolve from the initial incarnation. (Noting Daenerys growth from GoT S1 to date.)
TO
Most changed - Klaus has changed the most from season start to season end. Klaus goes from mindless slaughter to protector. He also will be going into next season dealing with repercussions of his actions. Something rarely seen in tvd/to.
Least changed - Elijah is the least changed of all the TO characters. Being my favorite characters I really dont have a problem with no change.
Tvd (S1-S5)
Most changed - Damon is probably the most change from his original S1 incarnation.
Least changed - Bonnie is the least changed from S1. She is 1 of 2 tvd characters I like.