Based on the "Critically Acclaimed" Binding of Isaac challenge "Dad's Home+" introduced in the Fiend Folio mod.
This challenge causes killed enemies to come back for revenge!
Enemies that you have previously killed will respawn in future rooms, ready for another shot (literally and figuratively).
Do you have what it takes to Enter the Gungeon under such peril?
No. No you do not.
This is a meme.
I do not think this is actually beatable, at least not on 100% spawn rate.
But you're welcome too try!

How to Use

Once installed, this mod adds a new command to your Mod The Gungeon console, dadsgungeon.
On it's own, this command simply lists whether the mod is enabled, and your current mod settings, however it has several sub-commands to alter these facts.

• dadsgungeon toggle This turns the challenge on and off. It is disabled by default, and will tell you it's new current state after running the command.
• dadsgungeon affects_bosses Toggles whether or not the challenge will allow boss enemies to respawn.
• dadsgungeon spawn_on_empty_rooms Toggles whether enemies will respawn in rooms with no enemies to begin with, like Chest Rooms.
• dadsgungeon spawn_on_backtrack Toggles whether enemies are able to respawn in rooms that you have already cleared. Set spawn_on_empty_rooms to true for full effect.
  and finally;
• dadsgungeon spawn_percentage x (Where x represents a number between 1 and 100). Determines what percentage of previously seen enemies respawns per room. 100% by default, but can be lowered to decrease difficulty.
• dadsgungeon enemy_hp_mult x (Where x represents a number between 1 and 100). Sets a multiplier for the health of respawned enemies, allowing you to make respawned enemies weaker if you want.
• dadsgungeon boss_hp_mult x (Where x represents a number between 1 and 100). Same as the Enemy HP Mult but for bosses, and is applied in addition to the enemy multiplier. 25% by default.

That's about it, have fuuuuun :)