Well, it is not an easy task to tell your friend that he is in a toxic relationship, is it? But the truth is that somebody has to do that. Although, you probably do not want to be the friend who cares about things that one probably should not care about. Or should?
Supposing he really is in a bad relationship, and he does not seem to realize how bad it is for him, someone should break it to him. Do not worry, we will show you how to do it right. Just keep on reading and you will definitely not mess up.
At first, you should probably make sure that the relationship he is in truly is bad. So pay attention to how he speaks about his girlfriend and about the problems they have. If they are constantly repeating and never go away, then your friend should probably back off as soon as possible.
So, when you decide that you should say something, you should probably consider when the best time to do so is. Just, remember one thing, take some time. Observe their relationship, see if anything changes, if not, then go with it.
Oh, and please, always have such conversations face-to-face. Not via Facebook or phone.
And remember, be gentle and prepare for any kind of reaction. Just give him some time to think it through.