For example, holding a grudge against his ex-wife Jennifer and her new husband--she thought he lied to her about murder, she divorced him while he was in prison, and he never had a chance to defend himself. Meanwhile, she married someone else and had kids and is happy.
The grudge makes sense. Crews' way of showing that anger is the fun part. He holds the anger inside and lets it out only in rigidly controlled dribs and drabs, through petty acts of vengeance, like leaving a horse on their lawn or repeatedly stopping them for minor traffic violations (particularly the new husband, who so far as we know had nothing to do with his wife's former relationship). Once, the anger, or possibly the grief at what he's lost, erupts enough that he kisses her. I need to watch that scene again to ponder everything going on there.
It's also clear Jennifer has some anger and regret, mostly demonstrated in the interview clips that intersperse with the plot. She doesn't express these things to Charlie; she doesn't seem to feel she has the right, and even if she did, he might not believe it, as he was the injured party. She moved on. Charlie wasn't able to; however much he changed in twelve years of prison, he was also in a sort of stasis there (unaware of cell phones shrinking and gaining cameras, Instant Messaging, etc.). To him, I suspect the pain is all still fresh, a wound he can feel only now that the worst wound, being falsely accused, has been covered. By the last episode, he appears to be trying to move on, but I doubt that he'll be totally successful any time soon.