Obviously, your friend suffers from a gambling addiction. And, as a result of his greed, he lost the winnings he should have lost. That is, he is also to fault for what caused it. When a gambler's gambling addiction is not properly handled, this is the negative result.
That example, if you see that even though you reminded your friend, he ignored it, and because of his addiction level, he doesn't know how to listen, that's because the self-control and self-discipline are gone, and in the end, your friend was still a failure. Do you understand?
If this keeps happening to a person then without a doubt we are talking about a gambling addiction, however there are people that can go through an episode like this and then stop gambling completely, in that case we are not really talking about a gambling addiction but simply about a series of bad decisions that eventually led to this outcome, and in that case that person can still be reasoned with, and if possible that person should avoid to gamble ever again as they have demonstrated they do not have the necessary control of their emotions to accept a loss and move on.