Info
Did you know there's secret difficulty values in Minecraft Java Edition? The game doesn't tell you outside of the F3 menu, but it scales up the longer you spend in loaded chunks. These secret values control many mob effects, such as spawning with armor, zombies having tools, zombies picking up said tools, having enchanted tools and armor, spider potion effects, etc. You can find all of the effects here.
This mod intercepts the regular time-based difficulty scaling and instead maxes it out the second a chunk is loaded. This mod should have little to no performance impact, but on some REALLY weak computers it could impact chunk loading times.
Usage
There's downloads for Fabric and NeoForge. Make sure you're downloading the correct version for your modloader. Fabric supports 1.20.1+, and NeoForge supports 1.21.1+
If you're running Fabric, you need to install any 1.20.1 version or later of the Fabric API.
Place it in your mods folder and it'll run without any extra setup. If you're playing singleplayer, it will apply to the internal server.