Hogwarts' Genius Assistant

In Harry's mind, "genius" is a very grand title. He rarely uses the word "genius" to describe a person, and even Hermione cannot match this title. But the Chinese young man was an accident. He deserved the title of "genius". Umbridge was a poor Defense Against the Dark Arts professor, but the Chinese assistant assigned to her by Dumbledore was one of the most powerful wizards Harry had ever seen. Not only was he familiar with the five elements of Chinese magic, but he was also good at combining them with weapons commonly used by Muggles to unleash astonishing power. Sometimes Harry really didn't understand why Dumbledore didn't let him directly be the Defense Against the Dark Arts professor?