Make an achievement called "Flawless Victory" or similar, and award it (that is, add it to Steam) when the player clears any floor without taking damage.
Might need a minimum difficulty (Normal?) and floor number (2?).
"Untouchable: Complete a floor with no damage."
Already part of the game, but it's among the easiest to get since there's plenty of ways to just skip to the next floor, clearing the current one without damage.
Risky Assassin on the other hand...