PhoenixMercurous

That did the trick, thank you.

Repairing had no effect, the same crash occurred after running repair.

I'm trying to run 1.15.2 with Forge and have had the same crash on all versions of 31.1.x I've tried, including the latest 31.1.19 and a couple others. The console output, including debug, is in the spoiler below: The emphasis on the error is my addition. This crash occurs with and without any mods installed, so it seems to be something with Forge itself. I've deleted the file it crashes on and let it reinstall it, which didn't work, and I've tried an uninstall/reinstall of Twitch, which also didn't work. I've made sure to install Java 8.x, and the crash still occurs. I've included the log file for this instance of the launcher. There doesn't seem to be a debug log specific to that instance, so I'm including the debug.log file from the \Minecraft\Install folder, which is the only debug file I can find. latest.log debug.log