Laezel easily. For one she feels like absolutely best fit for the story - As Gith infected by a tadpole of her peoples mortal enemy she has personal drive to cure it. Her personal dilemma also fairly naturally ties to the narrative due to major involvement of Gith. While I didn't find her personal arc particularly inspiring, it is well executed and satisfying to see play out. And has branching paths, which unlike lets say Shadowheart, I could see myself pursuing in the future.

From side characters? I don't know, I don't think there was an NPC I cared for the entire way through. Maybe the misterious cow. but it's more for the amusement than narrative reasons.