Wait till arya gets there
Arya is going to end littlefinger's run on the show. He's on her list. Only clegane made it off her list.
When did that happen? Doubt the guy is even on her radar yet. But he probably will be when she gets to Winterfell and finds out he gave Sansa away to a psychopath who raped her.
Beric and Thoros are also on that list, but they seem like good dudes who may be pardoned.