Link: https://en.wikipedia.org/wiki/Bartle_taxonomy_of_player_types

The best example i can think of this is in the game barotrauma, someone once asked "why do you grief?" The question itself is best answered by Bartle's Multiplayer Psychology maxim. We all lean toward some aspects of basic multiplayer motivations: Socialites, Explorers, Achievers or Killers. If you don't have much 'killer' (defined as someone who gets their fun by causing a negative reaction in others) in you, then it's hard to understand that motivation. Of course, few griefers will admit to that need. No-one is 100% one motivation, but Our Explorers lean toward Engineer roles, our Socialites are Medics or Captains, while our Achievers and more balanced motivation players tend toward Captains and Security.

This is the only way I can understand killers/griefers, as I struggle to see the emotional reward in the action.