Simba right after he gets back to the pridelands. Even though this is all on Scar, he is a part of it. If he didnt run, and if he just had gone home, this might never have happend. Of course he was quilty about Mufasa death and all, but as a cub no one would hold that against him. Even if what he did was the reason, as a cub he would be too young to understand. And with Sarabi and the prides help, he would learn. And later become the new king. And Scar would have never done this.