5. Izuna Uchiha
Izuna Uchiha was the younger brother of Madara Uchiha. Izuna along with Madara were the first Uchiha to awaken the Mangekyou Sharingan. Even though he was such a talented shinobi he was given absolutely no other powers as he was easily killed by Tobirama Senju which was surely a disappointment. We never saw his the ability of Mangekyou Sharingan either.
Gaara is the current Kazekage of Sunagakure and son of the previous Kazekage. Gaara has the extraordinary ability to manipulate sand at will and when he was introduced we all thought he would grow up to be more powerful but sadly he is still stuck on that sand manipulation and no new powers have been added to his arsenal.