Minecraft 1.12.2
Forge 14.23.3.2673
LLibrary 1.7.11

https://gist.github.com/Bulldog83/db97eb0666c67312c8e53aefacd1f22d

Can confirm a similar crash.

https://pastebin.com/NEay9bhu

@Sunconure11 This is an issue with LLibrary 1.7.10, update to 1.7.11.
@Bulldog83 Looks like the core jar was not extracted. Send a full log?

https://gist.github.com/Bulldog83/38098468e585bbf1d2d78aea0df00913

Mmm. LlibraryCore must be downloaded by LLibrary, right? I keep mods in separate structured folders and load via mod_list.json. May be, problem's in this? How I can download LlibraryCore separate?

I've taken it via new profile with only Llibrary loaded.

What about the debug.log? Also, have a go with the recommended version of Forge.

LLibraryCore is contained within the LLibrary Jar file -- Forge is supposed to extract it out and load it. You could try manually extracting it out.