DaemonUmbra

Rerun the Forge installer

Try the installer again

Try again

Have you tried again today?

Does a file named something like hs_err_pidXXXX appear where you ran the installer?

This is looking like a corrupted install, delete the forge jar, vanilla jar, and libraries folder and re-run the installer

Not a Forge issue, but it has been fixed upstream already, we just need LWJGL and Mojang to ship the fixed version now https://github.com/glfw/glfw/commit/2bc52ca82e46f6f238007b8e80b7253328bd080d

Remove RandomPatches

Can you provide a screen capture of the whole process, as well as your debug.log(more info in my signature below)?

Remove Optifine

Please provide debug.log (more info on where it is and how to provide it in my signature below, just expand the spoiler)

Try using Java 8 to run the game, we recommend AdoptOpenJDK

Please provide the server's debug.log using one of the paste sites in the "Logs" section of my signature below.

Are you sure you're using the version of Forge that the pack is designed to work with?

What version are you trying to use and are you sure you got the correct installer?

Are you tabbing away from the window while it's loading? If so, try not doing that.

To clarify why this doesn't work, that method assumes that the program opens the file simply by consuming it as an argument, i.e. a command in the form of: java [file] however, jar files are run with the form of java -jar [file]

Is this a published modpack or one you made yourself? If it's published please identify it. Could you please provide the world save in a zip?

Games shouldn't be interfering with this unless you're running them at the time. Are you tabbing out at all after starting the game? If so, try not doing anything after launching the game.

When this many configs are corrupted you might as well wipe the config folder

In the Curse client, click the gear in the bottom left, then click Minecraft under Game-Specific, where is your "Minecraft Modding Folder"?

Can you be more specific about "it doesn't work"?

That's not what I asked you to do. Why are you using JDK 12 btw, you should be using 8 for full compatibility with the ancient JRE that Mojang ships with the launcher. Are you using Mixins?

Please provide debug.log (more info on where it is and how to provide it in my signature below, just expand the spoiler)

What does this mean?