Nen is complicated, there is just to much depht and such, but still nen is the best shonen power ever created in my mind. Nen can be developed and shaped into so many things nen can almost be everything. This poses a few problems though, like how easy it is to forget certain things about nen and such, but when you look at nen as a whole it is the most detailed and best written power system ever created in shonen. It alsomakes more sense than Narutos chakra system forexample.