Animal Enemy (3.5e Flaw)
From D&D Wiki
Your character doesn't handle animals well.
Effect: Characters with this flaw suffer a -6 penalty to handle animal and ride skill checks. Additionally, they suffer a -2 competence penalty to AC when being attacked by wild animals.
Roleplaying Ideas: Maybe you wear too much cologne. Maybe your character tortures small animals for fun. This flaw applies well to evil-aligned characters.