I'd say probably, but not entirely sure. Even Tirek could potentially be capable of good, that doesn't mean he necessarily deserves another chance, with all the awful things he's done, nobody is required to forgive him, and it's likely they never would, and I doubt he would change, but it's possible.
I think "Pure Evil" people are far and rare. Someone who is pure evil is someone who causes pain to others, without any regret or remorse, simply for their own enjoyment or gain, is unwilling to change, and has no capacity for reason and kindness what so ever. Most people, even the really bad ones, have some good in them, maybe if they had a different life, or some good friends, or a different situation, they could have been better people. Maybe in their own mind, they are doing the right thing. Maybe, if they want to, they can even change.
That doesn't mean to always turn a blind eye, and I think at times the ponies are a bit too optimistic. Some people need to be locked up for others safety, and some need to be punished, but I think we take it too far in the other direction, a lot of people just aren't ever willing to forgive anything, we only see the negative things a person has done, and decide they are just "Bad", and that's all there is. A murderer really could, in other ways, be a good, kind, caring person. That doesn't mean we should set them free necessarily, but that doesn't negate the existence of "Goodness".
Good people do bad things, bad people do good things. Sombra, Chrysalis and Tirek all could have goodness in them, and all of our mane Six could have some bad parts to them.