How do you tell your friend that they're bad at being sympathetic or bad at comforting anyone?

I think that if you have a friend that is bad at being sympathetic or bad at comforting people is a tricky situation because you don't want to hurt their feelings. What I would do, is address that they are trying and you are grateful that they are making some sort of effort. However, you should say a specific part that they are doing wrong when it comes to being sympathetic or comforting. This depends on your situation but make sure you suggest the idea like "I think you should do this... instead of this." That way you're not forcing it upon someone and won't hurt their feelings.