Gavin is a typical bully who bullies anyone weaker than him; he also holds a grudge against John for throwing him out of a window. [1] In later chapters, Gavin is revealed to be among Wellston's strongest mid-tiers and has been known to boss around weaker students and force them to complete his assignments
I beleive a medium/ deep (more to the deepside) would fit this guys voice.

You need to be able to shout. No breathy shouts, or speaking, it doesn't work