You can try to delete local_settings.txt and maybe settings.txt files in directory near save folder (for me it C:\Users\User\Documents\My Games\Runic Games\Torchlight 2\). if it will not help, try to start game without mods (maybe one of used is bad). If it will not help, try to remove last save file). But before, switch off "cloud save" function in steam client

Delete the Settings.txt files within Documents > My Games > Runic Games > Torchlight II folders.

Verify files within Steam by right clicking the game name then choosing Properties then Installed files then Verify Files.