Hi Torgek, and welcome to this Sub Forum.
There have been more then just a couple of posts where users are seeing this Grimefighter keep running with no apparent instructional dialogue to inform the user what is going on or where you are with the process??
Quite concerning, To my knowledge, there has not been any definitive direction/instruction From Avast as to what a user needs to/should do when Grimefighter runs/is running on a persons PC for 70 hours!
I am not sure what would ocurr if the OS was shut down, and can understand the fear.
Other users with similar issue posted here, have left the process run.
Good luck