The fight scene at the end with the monster mutant was boring and drawn out
I actually agree, I was expecting a huge fight like first the mutant, then after he dies, he comes back in the form of a demon at least 20 stories high, very typical of a Ninja Gaiden final boss.
The whole anime however reminded me of Ninja Gaiden 3 really. If anyone's beaten the entire trilogy on the NES, one may recognize the setting of the first two is demonic fantasy, ancient castles, bats etc, and then in Ninja Gaiden 3 it starts off with the demonic setting, but then starting at the halfway point of the game, the setting gradually turns to sci-fi.
Because of that transition from human to mutant, Ned Friedman kinda reminded me of NG3's H.P. Clancy.