That's pretty bad. I know some folks on here just go ahead and trim those areas off before they become infected...I'd find it hard to do unless there was absolutely no blood supply left. How about you try massaging that comb lightly with some castor oil and see what becomes of it? Could be that just the outer layer of skin will slough off and the outer tips, but a good massage and the antibacterial properties of the castor oil might help to restore some of the circulation and prevent infection. The castor oil is also good for the skin and may help prevent any further damage.
That last pen of cheap meats was showing several blackened and shriveled tips on the combs when I go them...those that were the worst got a gentle massage of castor oil and they brightened right up in a few days. Later on when it was really wet and cold out I saw a few dark tips again but they were gone the next day and nothing came of it. All those leghorns and other large combed breeds came out of our weather down in the teens, in their very open air coop, without any true frost bite...nice, red combs all.
It's not that beautiful bird in your avatar, is it? If so, that's a real shame.