https://gist.github.com/kreezxil/3a063754bfb5e8366318b0297e3e5fa9

1. installed mod
2. booted client
3. got the crash
4. reliable for me

mc: 1.15.2
forge: 31.0.1

Please provide your latest log file, as the crash report in this case does not actually contain the source of the issue due to MinecraftForge/MinecraftForge#6374

Were you able to run all the other mods before installing mekanism?

took your mods out and I was able to start my pack.

putting your mods back in to generate the report files again.

and I can't get it to do it again.

it is either a one off, or one of the other mods I removed was conflicting with your mods.

So I'll close this now.