Diego Ijeiska

He was the headmaster of the Hero Academy and teacher of the selective class Jerga-Kanon.
Like most of his elite students, Diego is arrogant toward the Demon King Academy and its students. This obsession with human superiority is demonstrated when he belittles Delsgade's students at any given opportunity, going as far as cheating during magic demonstrations and exams to humiliate them.

(Source: Maou Gakuin Wiki)