To me, intent is everything.
Reprehensible things can and have be done through indifference, ignorance or emotion. So I ask myself:
1) Was this done with malice, intent to harm or through pettiness?
2) What brought them to that step?
3) How have they chosen to move forward/atone?
While question 3 holds the most sway over me in the end, a positive answer to question 1 necessitates an exponentially damned good answer to question 3.