Question: For one of my character's arcs I plan on having him, for lack of a better term, become kind of a jerk after being disillusioned one too many times. Because of his new more confrontational attitude, he drifts away from his friends.
However, I do want to have him regain his original morals and reconcile with the main character after the main character gives him a taste of how much he had hurt the people who care about him in a kind of "if you kick me while I'm down, I'll do the same to you, but now I consider us even."
But I'm not quite sure how to make the reader acknowledge that this character is being just plain mean yet not have them dislike him so much that they wouldn't accept his reformation later on.Answer:
If you want the reader to see your character as mean, go ahead and show him doing mean things.
Readers will accept his later reformation as long as you show what causes his reformation. As long as they can understand why he changes, and what made him mean in the first place - because the evidence is illustrated in the story - then it will make sense to them.
The key is to not leave out any step in the character's arc. Don't have him suddenly behaving differently for no understandable reason. Show the forces driving the change, and crisis that forces the change itself, and the resolution of the crisis.