'Phoenix Jones' is up there for me. Apparently Washington has some weird laws where people can just beat the shit out of etch other in front of cops and its ok. So this guy starts dressing up as a Superhero and fucking people up. Then starts a group called the 'Rain City Superhero Movement' of all former military and MMA fighters and they patrolled the streets.

Marvin Heemeyer probably takes the cake for me though. A corrupt small town tried to shove him out of business with backdoor deals to put in a concrete factory. He bought a bulldozer to rebuild a road to his small business and they blocked him from making a road while slandering him. So he turned the bulldozer into a 'Killdozer' using concrete from the concrete factory that was trying to force him out of business and take his land.
Then he went to work. Messed up the concrete factory, destroyed the Mayors house that got rich screwing him and went after a number of other city buildings. He always told them where he was headed so nobody but him got hurt but there was just such beautiful irony in it all.