Just beat it, amazing. Great final boss. Quite easy on Ultra Violence but Im going back to Nightmare now.
I tried Ultra Nightmare and I beat the first level to get the achievement but that was it. I dont know what kind of cyborg can actually beat the game without dying once on Nightmare level (+ more I believe). That fight on the VEGA Level when you get off the train? One of the hardest fights in FPS single player history for sure. For sure for sure. Can't imagine it on Ultra Nightmare.
100%'d everything and I want more. Playing user generated maps now which has a cool system where people can easily make their own maps and campaigns. God damn this game is A+. Best FPS in a long time.