I recently installed a newer version of forge 1.12.2. The game launches fine, but when I attempt to start a world the game crashes. According to the people at forge, quark may be the issue. I have attached a copy of the complete game logs at the time of the crash:
latest (1).log

I would firstly update your java to the latest which is 1.8.0_171 not 1.8.0_25 that you have.

You are currently 146 versions behind.

Also, from looking at this, it looks like a multitude of issues, not just Quark. You are also using a massively outdated version of Optifine too which probably isn't a good thing knowing how volatile Optifine can be.

I would correct those 2 things, then try again.

I have updated java and optifine to their latest versions -- and even updated Quark and AutoRegLib -- yet I am still getting pretty much the same error as before. Do you know what else it could be?

Try looking for updates for ALL your mods first, then make sure your launcher profile is actually using Java release 171 instead of 25.

Post new crash logs if the issue reoccurs.

It's working now. It started acting normally once I followed your suggestion and updated all my mods. I suppose quark didn't have much to do with this after all.