The supreme hunter battle was a bit challenging. Bad enough that he did massive damage and took little damage, but then I had other infected running around trying to kill me and then the military showed up to crash the party. Took me awhile but I beat him. Did the next few missions as well. Stopped right after the convoy mission where I'm escorting the bloodtox truck. Almost had my tank blow up during that one, but made it through with barely any health left.