“Clubs” is a very accurate moniker for what the Killer likes to do. They thrive on competition with other players, and prefer fighting them to scripted computer-controlled opponents.
Single-player appeal to the Killer
These gamers love to sow destruction, so games that are high in carnage, action, and destructible environments are definitely a plus. Many of these gamers also enjoy the opportunity to depart from the norm of being “the good guy” who comes to save the day. Instead, they will play on the side of evil or conquest. On the flip side, Killers also represent the archetype which is most interested in affecting their environment, so sandbox games in which they can take a direct hand in building (or destroying) a virtual society will appeal to them as well.
Multi-player appeal to the Killer
Causing mayhem among computer-controlled people and things may be fun to the Killer, but nothing amounts to the joy of pitting one’s skills against an actual player-controlled opponent. For most, the joy of being a Killer results from a friendly competitive spirit. They’re in it for the sport, trying to read their opponent’s moves and generally acting with honor.
For others, it’s more about power and the ability to hurt others. One such example is “ganking,” a process where the Killer takes their strong character to a place where inexperienced or weaker characters reside, and proceeds to kill them repeatedly. Stronger enemy players arrive to help, and the Killer either waits patiently or stealthily sneaks somewhere else to repeat the process. These Killers love to have the notoriety of being someone that should be watched out for, or even better, someone to be “Killed on Sight.”
In other contexts, Killers are also active in the social and economic sides of a multiplayer game. Market control appeals strongly to Killers, many of whom have a natural talent for reading markets (likely an extension of their common aptitude for sizing up strengths and weaknesses, vital to their play style). Social Killers tend to be guild, clan, or community leaders—or trolls. Many make the mistake of thinking Killers are antisocial or without friends, but this isn’t too often the case. Even the more hostile and aggressive Killers can inspire a sort of hero-worship by less-talented Killers or Achievers; and, believe it or not, some Killers are actually genuinely nice people who simply thrive on competition. In either case, a bored Killer can be a threat to the community, as their natural drive to compete and sometimes (or frequently) abrasive attitude will push them to stir up trouble even when they don’t really mean to.
(Source: Bartle on Wikipedia)