Deuteragonist. 17 lines.

Mack copes with his dead-end future by trying to convince himself that he's too cool to give a shit. He's naturally a person with a lot of passion and verve, and maybe they might have done him well if he'd been born to a better household, or at least a less destitute one. As things are, he papers over his poor home life and horrible performance at school with false confidence and pride. He genuinely enjoys movies and comics (despite an inability to distinguish between "needlessly dark" and "deep") and tends to identify with edgy, "alpha"-type characters to a concerning degree to validate his conceptualization of himself as a cool, tortured badass rather than a sad, lonely kid.

He does genuinely care about Joey, though he's far too emotionally constipated to express that in any healthy way. The exaggeratedly confident manner in which he comports himself is mostly to mask his own insecurities, but it's also an attempt to make Joey laugh-- one that used to work. He's not dumb; he's aware of how awkward Joey always seems to look in his presence now, and he hates how shitty it makes him feel. He tries to make things normal between them again by leaning further and further into his overblown bravado, hoping to coax something besides distant discomfort out of Joey without realizing that he's only making Joey even more uncomfortable.

He finds the prospect of scaring Joey attractive and repulsive in equal measures-- on one hand, there's schadenfreude in acting on his deeply-buried, not-quite-conscious resentment towards Joey for having everything he wishes he could have, not to mention the intoxicating feeling of finally being in control; on the other, he finds the prospect that one of his oldest (and perhaps only) friends can't see past his tough-guy front and is actually afraid of him horrifying.

Joey may be the protagonist, but Mack is by far the most demanding role in the film. Besides having the most lines, he requires a huge range of performance, from semi-friendly ribbing with an undertone of bitterness to full-on desperate screaming. His voice is naturally a tad on the higher side for a teenage boy, similar to Joey's, but he speaks in the lower end of his register to try to sound tough (with varying degrees of effectiveness).