After selectively disabling certain mods at a time, I found that the combination of the 2 mods (3 including libraries) below causes a crash, near the end of loading. I also tried adding OptiForge, in hopes that it would fix the crash, but it does not.
All mods are the latest version compatible with 1.16.5 as of this time.

Game Log

https://gist.github.com/JawboTau/288c145f334ede8d33b7c163555195d4

Mods

Basic Info

• OS: Windows 10
• Forge Version 36.3.34
• Minecraft Version 1.16.5

Remove Optifine, I'm not working around their bugs anymore.