Reviving Enemy/Playing With

Basic Trope: A video game enemy which can become a threat again after being defeated.

Straight: Bob's armies include Mecha-Mooks and The Undead which are capable of repairing themselves sometimes after Alice manages to damage them enough until they fall down.
Exaggerated: Bob has saturated the battlefield with an advanced type of Nanomachines and necromantic magic which repair any of his machines and minions in a matter of moments, even if Alice smashes them to pieces or burns them into piles of slag.
Downplayed: Alice is an Actual Pacifist who only knocks out Bob's mookss, meaning that they wake up after a while. The player can kill them, but this upsets Alice and leads to a Nonstandard Game Over if it's done too often.
Justified: Bob's mooks are either undead or robotic and designed to be easily repaired. Creating a self repair system was fairly easy.
Inverted: If Alice is defeated, she's sent into a "Danger Mode" where she'll die if she take much more damage but will regenerate to full health if she can get to safety.
Subverted: Alice is told to burn the corpses of zombies to stop them rising again in the tutorial...only to be told by a mildly irritated Bob that the laws of magic make it impossible to revive a corpse that's already been revived and defeated.
Double Subverted: Bob's developed a new spell that allows him to make his minions rise as something even more powerful, as long as Alice doesn't damage the corpses any further while they mature for a bit...
Parodied: The reviving enemies are introduced by a cutscene were Alice keeps slaying the same mook over and over again until someone tells her how to make it stick.
Deconstructed: Players find having to deal with these reviving mooks extremely annoying.
Reconstructed: ....at least until Alice unlocks the skill that allows her to shut down robots permanently and destroy zombie corpses before they can rise again.
Zig Zagged: Some enemies can come back, some can't. Some only come back some of the time.
Averted: The game uses Respawning Enemies instead.
Enforced: "We need to keep older areas dangerous, but the player has to clear them of enemies to continue." "Just have them get back up again after a while until Alice has the holy sword to slay them with.
Lampshaded: "Oh great, The Undead, Ooo, look at me! I'm so cool because you need a special item to kill me properly! show offs!"
Defied: Alice has her weapons enchanted to disintegrate the corpses of fallen enemies, ensuring that Bob can't use them to make zombies or cyborgs out of his fallen mooks.
Discussed: "Careful, they might get back up if you don't burn the corpse or use something holy. Tricky business dealing with the undead. I remember once when I was raiding a tomb..."
Conversed: "What? You mean I can't kill those zombies yet! I'm calling Fake Difficulty!"
Exploited: The developers make the Disc One Nuke unable to permanently defeat enemies in order to make it less useful as the player progresses.
Played for Laughs: The reviving enemies are clowns who simply suffer Amusing Injuries when they're defeated. Their weakness is a Pie in the Face, which irritates them and makes them leave.
Played for Drama: Alice is the main character in a survival horror game. Having to constantly fight off or flee from the enemies puts a real strain on the player's (limited) resources.

I cleared out the main trope of enemies a while ago, but it looks like you have to go back to it; Reviving Enemy. Don't worry, I'm sure it's still safe.