Hello!
Simply, I would not do it. Benjamin Rush had the first citation of the phrase, "Two wrongs do not make a right." If it were my cousin were to act on his or her plans to vandalize the property, and he could get in serious trouble. In many states, you could earn up to a year in local jail. If the damage were severe, and unreplaceable, it would be charged as a felony. The bully was very wrong, but stooping to the bullies level, will not help you in the long run. Your cousin could end up losing important life functions, if caught, like the ability to get into college, or getting a job. Having a criminal record, is a difficult factor in job finding research. I would tell my cousin to think before you act, and choose future over revenge.
waffletowne.