A creature is a legal target for Power Word Kill if it doesn't have any of these four creature types. If it has one of these four creature types, it's not a legal target, even if it also has a creature type that's not among these four. For example, a Demon Rogue is not a valid target for this spell.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.