Into stuff like full saccing the guy that you think could potentially kill you one day in the hope he'll rage delete. Logging on when you have buddies but not if you don't. Not facing opposition even when you have the upper hand, if there's slight risk, but gaming mercilessly when they are alone etc.

And then beyond that is the outright cheating. ooc groups to get gear. Ooc groups to protect you etc.

There's also just the desire to play broken builds and abuse whatever it is that makes them broken.

Plus there are technically legit ways to kill people outside of your pk etc. Like track a mob who is aggro to all even when he's following your trail, into a lowbie area. Or repeatedly using repel undead as a hero to swamp groups of mid level characters in the mausoleum.