Versions

Betweenlands version:

3.4.0-universal

Forge version:

1.12.2-2.6.0.79-universal

Singleplayer or Multiplayer:

Singleplayer

Installed mods:

Technician's Survival 2 modpack

Link to full crash log

https://paste.dimdev.org/cihejadiwa.mccrash

Description of the problem

How to reproduce:

1. Start Minecraft
2. Crash

Expected result:

I expected the modpack to actually start so I could try it out.

Actual result:

The game crashed without even starting.

Modpack Link from Curse Forge: https://minecraft.curseforge.com/projects/technicians-survival-2

Installed the pack and it's working without any problems.
Make sure everything is installed correctly, e.g. try reinstalling the pack.
I've also heard that installing modpacks in OneDrive can cause problems, so if you're doing that install the pack somewhere else.

Maybe it's because of the Twitch launcher...
because I just got this when I tried: https://paste.dimdev.org/wuzebixire.mccrash

Probably not, I installed it using the Twitch launcher.
Did you reinstall the pack like I suggested? Did you manually modify any of the downloaded files?
Also, please post the whole log so I can have a look at it.

I reinstalled as suggested, modified nothing, and... There... the entire crash log.

Edit:
https://hastebin.com/cowugebuko.rb

Can you upload the debug.log that you can find in the logs folder in the modpack instance?

latest.log

That's the only log in the folder.

Do you have multiple instances running of the pack or some other program that would interfere?
Try restarting the twitch launcher (right click, Quit or Exit or whatever it is), make sure no process is running (with for example Task Manager).
If that doesn't work I'm not sure what's the cause, possible very long fetched but maybe restart the computer if you haven't (don't think it matters but you never know)?

Because from the looks of it in that last log file some other process is using the file need to load and preventing forge to get access to it. Also from the looks of it ImmersiveEngineering would be affected in-game if it would boot as it's also being denied loading of its core.

No, I've never run multiple instances of Minecraft, modded or not. And I've rebooted twice since this started with no luck.

Well... dunno how it happened, but another attempt got past the initialization phase... then crashed.
Attaching crash log...
crash log.txt

That did it. Got it running after updating Java. It's slow to load, which isn't surprising given the mod count, but it's working.

Thanks for your help. :)

That crash is of Java itself and not minecraft directly. Looks like foamfix is part of the issue or just a false positive.
Try updating to the latest Java 1.8 (1.8 Update 191).
Other than that I don't know what could have caused it.