Dodging is key here.
This brute hits like an absolute truck, so dodge his attacks and go in for one or two hits. Don't get greedy as he can easily take you out with a few punches, especially if you haven't been levelling up much.
Not only do you have to worry about him, but he can also spawn a shadow clone that you can not damage.. but it can damage you, so again, DODGING. IS. KEY.
Use ultimate attacks whenever you can to help speed this fight up!
On top of this, the games lighting in this boss arena can get pretty blinding (I hope this gets patched) meaning there will be times you can't see him at all; Just keep dodging and moving the camera until you fix the lighting... If not for this issue, the boss would be a lot easier.
EXPLOIT: If you ever feel too weak and wish to level up fast WITHOUT killing NPCs there is a nifty little trick you can do; Plug a USB keyboard into your console, go to a bed to level up, select ANY power and once in that powers tree.. hold down P on your keyboard and you'll gain xp as long as you hold it down. You can be as powerful as you wish!
Any questions, just ask!