Using Minecraft 1.12.2
LWJGL 2.9.1
Forge 1.12.2-14.23.2581
Launching game via MultiMC, v0.5.2-1096
Disabled all Core mods that were identified by initial crash, disabled mods dependent upon those, then disabled additional core mods, and finally mods dependent upon them. Also disabled Optifine. Except for Optifine, I only disabled mods identified as core mods by the Forge crash report or mods Minecraft claimed were missing required dependencies. (So I still have a ton of mods being loaded, but they are not identified as "core" mods in the crash report.)
Despite doing the above, Minecraft still crashes while loading.
Crash Report: https://gist.github.com/Zarepheth/a3b1446c942b2dedd886f0b5018de4a2
