1.7.10 Crashing upon entering Multiplayer (no forge, normal mc) [duplicate]

This is an issue that occurs when downgrading from Minecraft 1.8 or higher without deleting your options.txt file or correcting its renderDistance entry. You can fix this by either deleting the file or changing renderDistance to 12 or lower. To do this, first open the game directory of the profile as described in this picture (sourced from here).

After that, find the options.txt file and either delete it or open the file in a text editor and change the line that starts with renderDistance to something like renderDistance:12. It can be lower, but don't increase it beyond 12. Save the file and launch Minecraft, and it should start.

Sources:

• MC-38527
• MC-67266
• MCX-475141 which contains an almost identical stack trace as well as a link to instructions for deletion.
• Mojang's help page detailing finding the instance folder