I don't think that there is just [u]one[/u] most destructive emotion. Here's some of my examples. Despair can hurt. Say you and your parents were abducted by criminals, who were going to kill them as you watched, knowing that you couldn't do anything to help them. Regret. It can cripple one's mind over many various reasons. Say you you were drunk and you cheated on your husband/wife, who impulsively divorced you. Boom; regret. Betrayal is a big one. Your best buddy since kindergarten just framed you for an incident that occurred at work, costing you your job (at least until you prove yourself innocent). Those are just a few of the ones I thought of that cause the most damage.