DaemonUmbra

Provide a log with just Forge

Please do not hijack other people's threads, if you have an issue make your own thread and include logs Edit: You already did, moving this to your thread.

It sounds like you're telling Minecraft to use more RAM than is available

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

Use the new native launcher

Does it happen if you run the server locally?

Looks to me like you're missing a Scala library, please read the installation instructions for each of your mods.

1.8.9 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

You're getting at least some of your mods from repost sites that can't be trusted, and I highly doubt you have 500Gigs of ram in your PC

That error is indicative of running Forge 1.12.2 on Java 9 or later, Forge 1.12.2 only supports Java 8

My signature contains information on what file I want and how you should provide it

Run this once then try again https://johann.loefflmann.net/en/software/jarfix/index.html

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

Sky Factory doesn't get published to Technic, please install the Twitch Client to get it.

It's actually not using much memory, you're just not giving it much. https://minecraft.gamepedia.com/Tutorials/Setting_up_a_server#Configuring_from_the_command_line

That starts a vanilla server, you need to run the Forge jar to start a Forge server

https://whatismyipaddress.com/ (You want IPv4) How are you starting the server?

"You didn't help these people, you asked for more information instead, therefore you are a horrible person" Whaaaa?

Can you connect to the server with your own client via localhost?

What happens when you run the forge jar from the command line?

Connecting to localhost would make sure that the server is actually up in the first place

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

localhost in minecraft, this will only work if you're on the same machine as the server

Looks to me like you're missing a mod