If you’ve installed mods, restart your game, and receive a Fatal Error that prevents you from navigating back to the main menu to deactivate mods. This is how to manually reset your installed mods.
Go to Steam Library
Navigate to your Steam Library and click on the options cog to bring up the game menu. From there, click on the Properties tab and navigate to Local Files. Then, click on Browse. This will open up the relevant folder in File Explorer.
Steam Library> Game Properties> Local Files> Browse
Delete a File
From this point, Steam should have opened up the Mechwarrior 5 Mercenaries folder. From here, you want to open the MW5Mercs folder and navigate to the Mods folder. Inside, you will find a file called “modlist.json”. This is the active list of mods being applied to your game. Delete the “modlist.json” file. You should now be able to restart your game and fiddle with enabling individual mods to figure out which mod is crashing your game.
Mechwarrior 5 Mercenaries> MW5Mercs> Mods> modlist.json