I already told him but ...

Giving feedback in an effective way is not easy, for sure not for folks in many Asian countries. After a training and practice session, most at least will give it a try. What I often hear a week later is "I already told him but ...". The most important part of giving feedback is not the actual moment in which you give the feedback ... It is what happens after that. There are two possibilities. Either the person will improve (even if only somewhat, or temporarily) or won't. And what you do at that point is more important that the actual feedback.

If the behavior/issue/performance has improved ... let them know ! There is nothing worse (really) than someone taking feedback for real, working hard to get better and then start to wonder if anyone really noticed it the improvement.

If the behavior/issue/performance does not improve ... the same goes ! Way to often I see folks give up after just one feedback. They conclude that the other person doesn't want to change, is not capable of changing or just doesn't get it. I already told him but ... Expecting things to change right from the first feedback is not realistic. Lack of follow up can be interpreted in different ways. It can be seen as "it wasn't really important after all" or "my manager is not courageous" all the way to a break in the relationship with both avoiding the deal with the lagging issue.

If you have children, and they don't do what they are supposed to do despite you telling them, you don't simply give up ! Repeat repeat repeat.