Bully Vendetta (3.5e Flaw)
From D&D Wiki
But you go too far and often overreact to bullying. If you notice an NPC bullying some living thing, person, animal, etc., your status towards them becomes hostile. If a PC bullies some living thing, you become unfriendly and immediately attempt to stop them.Understand you HATE all bullying and cannot stand seeing someone overpower someone weaker than them. This means that you are just as likely to come to the aid of an evil being as a good, as long as they are not your enemy. You may attempt to ignore an instance of bullying with a Will Save DC 15 plus 1/2 your hit dice; however, you cannot ignore two instances of bullying that are within an hour of each other, even if they are unrelated. Ignoring an act of bullying puts you in a really bad mood. You suffer a -2 penalty on diplomacy, sense motive, and bluff checks. Also, you are considered distracted. These negatives stay in place until you do something about the bullying or stop another act of bullying.