First post but I have to rant this. I hate this topic.
I keep seeing people ask "could Charlie redeem this person?" or "Can (insert any disliked character) be redeemed?". Its a pointless question because the answer is yes. Now before you hate me I have to say this.... yes anyone can be redeemed BUT only if they choose to or are given the right circumstances. No one in this show that is getting better has been fighting against getting better. They're all growing by having something to get better for, they have been choosing to do good and be kind for themselves.
The Hazbin Hotel is a place you choose to go to and you choose to try out its bullsheet therapy. Pentious, as sad of a vilian as he was, couldn't have been redeemed if he didnt choose to make friends and to fight for them. He had a cause and chose to take action. If anyone, including Valentino, Alastor, Husk, Angel, and begrudgingly Susan, decides to work twords redemption and makes a stand against their wrong then they'll be redeemed.
Redemption doesnt make their actions go away and we will continue to judge them by it, but it isnt impossible to redeem them. Thank you for coming to my ted talk.