Easily, the thing I hate most about WoW is griefing lower players. That is, having a higher level player cause you trouble for no other reason than he can. Sure, you could move to a non PvP server, but PvP is a challanging part of the game, when handled right. Otherwise, why even go online?

WoW player analyzes PvP cruelty - Joystiq - www.joystiq.com

But the constant revenge as a level 60 character on those beneath your level is a little too extreme. Does Hellacow see himself as a senior fraternity member hazing the pledges? I hated those guys in college and I hate them in World of Warcraft, too.