A critical error has occured and must be terminated.

I recently got back into LoL. The first game i try playing it said that there was a critical error, and avast took it as a "potentially harmful file" clearly, it isn't. so I disabled my avast thinking that was the problem. it still persisted, i disabled firewalls, it still persisted. I'm not sure if it is my OS (since recent update windows 10 can't do stuff properly) or something wrong with the installation.