The problem is that it is not your fault. You are and were not responsible for keeping him alive, especially not since it sounds like you would have had to take a lot of abuse to do so (lying and cheating is not a "normal" part of depression, and while depression is a terrible disease, it does not absolve someone of taking advantage of others). In the end, we cannot be responsible for other people. If he was standing there with a gun to his head and you said "Oh, that's too bad but they're having a sale on Chang over at Cheap Charlie's, bye" and walked out; if you handed him a bottle of pills and said "have fun"; if you said "yeah, world would probably be better off without you"; that would be one thing, but no, it is not your fault that you could not and did not babysit another person 24/7 (especially since doing so would have been to your own detriment) for fear of what might happen, and there is nothing wrong with protecting yourself against someone abusive. Do not feel guilty. You did what you could, and even hung on longer than family... in the end, you could not work miracles. There is no guilt in that.