Erronlol

I'm using forge 1.12.2 and it launches perfectly without mods. However when i try to launch forge with pixelmon 8.1.2 everything loads all the way up until "finishing up", then it stops responding and i have no clue about what to do. I give the launch 4gb memory to work with, i've tried 2gb aswell but the issue still exists. Any help would be appreciated.