Jacen solo is just like most characters I have read about in books and seen on film. They are always trying to save the world but at a certain cost that will affect them. They have to turn to the dark side.The reason why Jacen Solo turned to the dark side was to save the galaxy from the fate he foresaw.This reminds of Harry Potter’s mom who made the ultimate sacrifice so that her son can live. Ib this case the only way to save the galaxy was to turn evil.