[hamidpalo]

You're thinking about it wrong. It's not about the complexity of code or any measure thereof, but a simple communication issue.

Telling someone that their code is too complex can very easily be interpreted as a personal affront, especially by more junior developers. It can very easily communicate that they are a shitty developer and don't know what they are doing. When that happens you will get nowhere.

In that situation, the other person feels that they have to defend themselves. They get myopic and unable to see whatever argument you present. They simply will not accept it, or if they do they will resent you for it.

The best way to go about it is to acknowledge their efforts and validate their thinking. Look at why the code is the way it is, and try and understand why it's written that way. Approach the situation not as "I am right, you are wrong" but as "I don't understand this part, can you explain it to me." When they explain and you think it's complex say something like "Ah, yes! That's what I thought it did. It seemed a bit complex so I was wondering if it did anything else. Have you considered x or y?"

The more opportunities you allow to the other person to save face, and the more you value their efforts and work the further you will get.