It isn't going to be a sexually oriented game... I am inspired by Corruption of Champions in that it has RPG conventions but centered around beating people senseless rather than killing them.
In lieu of killing, I'm thinking the usual term would be "defeated." Killing can be done, if you really want, but is more messy, prolonged, and difficult.
Most monsters are either magical creatures or significantly huger than humans.
- Dragons and giants might often be encountered laden with stolen loot they're taking back to their horde, and defeating them results in them dropping what they may have stolen and making a run for it (and if they're prevented from fleeing through PC effort, will begin to SERIOUSLY fight in a frenzy, which isn't something that is going to be a comfortable experience for most PCs). You are basically stabbing such creatures in the foot until they decide "fuck this I'm going home." Unless in a frenzy, they are more likely to rob the PCs as well than be interested in killing them.
- Zombies and possessed are easier to revive/exorcise than to kill, and killing a possessed also frees the demon within, who will be significantly more powerful than before.
- Creatures like wraiths, ghosts, and even vampires are more parasitic in nature than killy; they typically attack by clinging and siphoning away life force, blood, etcetera, killing them causes them to turn into vapor or mist for a time.
- Goblins are excellent illusionists, thiefs, and rascals. Defeated goblins simply vanish, either teleporting away or being revealed to be illusions in and of themselves, and a goblin attack may often similarly have illusions of monsters, and illusions are themselves a category of monster. Of course, if you really desire to kill them for good, something like Dimensional Anchor would work.