There are many characters in Naruto who needs more developing, including secondary characters and others. Some lost their growth do the lack of screen time. While others are simple forgotten for the lack of the better word. When I say developing I don't mean only on their ninja skills, but also their personality's. Their are many characters who almost have the same personality like in the first part of Naruto. Some had development in ninja skill while they lack personality growth, while those who had some personality growth lack ninja skills.
Sakura Haruno: While she improved her ninja skills on the beginning on the part2, she didn't have any other skill development. Even trough it's been hinted by Kakashi that she has talent to surpass Tsunade.
Spoiler for manga:
Neji Hyuga: He was supposed to became something like second rival to Sasuke in the first part do to their bloodlines. While he had almost major character development in part 1. This has been ruined because the lack of screen time he gets. He stayed the same as in part 1 in skills and character development. He is also the one who knows the best to use the byakugan, just for this he needs to get more development, yet he is being ignored.
Shikamaru Nara: Even when he shown, it's almost always about his intelligence. His personality hasn't changed much. He still thinks everyone/everything
is troublesome. His ninja skill still remains the same. This is the problem because we have some characters with new power levels, while he and others remain the same. This will also limit their screen time in the future. I may be OK with his personality being almost the same, but I would like to see him developing some/more ninja skills.
And I can say about more other characters But I don't have time right now
Sakura Haruno: While she improved her ninja skills on the beginning on the part2, she didn't have any other skill development. Even trough it's been hinted by Kakashi that she has talent to surpass Tsunade.
Spoiler for manga:
Neji Hyuga: He was supposed to became something like second rival to Sasuke in the first part do to their bloodlines. While he had almost major character development in part 1. This has been ruined because the lack of screen time he gets. He stayed the same as in part 1 in skills and character development. He is also the one who knows the best to use the byakugan, just for this he needs to get more development, yet he is being ignored.
Shikamaru Nara: Even when he shown, it's almost always about his intelligence. His personality hasn't changed much. He still thinks everyone/everything
is troublesome. His ninja skill still remains the same. This is the problem because we have some characters with new power levels, while he and others remain the same. This will also limit their screen time in the future. I may be OK with his personality being almost the same, but I would like to see him developing some/more ninja skills.
And I can say about more other characters But I don't have time right now