My friend is almost fatally depressed, what can i do to help him?

The thing about depression, is the person needs to see that they have a problem that needs a solution, which ultimately only they can provide. You can help and support your friend, but he may well just use that as an excuse to sink even further. Try and get him to focus on the positives in his life and do things that proactively help him see thi. Even if it is small steps, it can be enough.