So I tried to search the issue but came up with nothing, the most I could get was some people having a mod location between the colon and the word "failed" but I seem to have nothing there. I am also making a modpack of my own, and tips are appreciated!

 

Add the crash-report or latest.log (logs-folder) with sites like https://paste.ee/ and paste the link to it here

 

Got it! Here you go
https://paste.ee/p/5P6jZ

Also the version is Forge 1.20.1-47.2.17 if that helps.

Make a test without Essential

Tried it but same thing happened.

 

Add the new crash-report

 

Here it is
I removed some mods that had errors
https://paste.ee/p/WQ6PI

And without prism?

I haven't tried that yet let me go ahead and do that real quick

Same error. Posting the new crash report in a sec

https://paste.ee/p/bnxx0

Here it is

Should I re-add Essential and Prism now?

I have no idea - looks like some kind of connection issue

Make a test with another Launcher and/or with disable firewall and antivirus program

Also make a test with a pre-configured modpack

Tried with CurseForge, same error.

Make a test with the AT Launcher - if this is still not working, add the new log from this launcher

Also make a test with a pre-configured modpack there

At Packs, search for a Modpack for 1.20.1 and install it / run it

I did as I usually do and take out sections of the mods in my mod folder at a time and I just now got a change
The error disappeared when I took out G through Q.
About to do some more testing to see what mod is causing the problem.

Mod called Impactor

Specific file name : Impactor-Forge-5.2.6+1.20.1.jar

Removed Impactor. 
Error is gone.

Wth new problem
Whenever I try to start a singleplayer world I get this message?