Oddly enough, given the absurdity of the feat, I don't think the most impressive part about this clip is Myles Garrett going from flat-footed to jumping multiple feet in the air with the free-weight equivalent of a prepubescent teenage boy in tow. Rather, I think the most impressive part of this clip is that, somewhere along his path to NFL stardom, the Browns' quarterback crusher just assumed he was strong and agile enough to be able to do so.
Of all the exercises out there, I'd say a box jump is one of the few that you don't even consider attempting unless you're at least 90% certain of your ability to complete it. I imagine that also stands true for professional athletes who, while inherently more confident, are just as likely to fall backwards and bust their ass or bang their head if their eyes do happen to travel higher than their vertical. Therefore, there was a time when Myles Garrett instinctually knew himself to be capable of adding injury to injury, in the form of weight to body mass, while spitting on the laws of science and standing to tell the tale before even successfully doing so.
That time probably wasn't the one we just watched. After all, he seemed a bit too casual in his otherworldly athleticism, as if he were a seasoned vet of such superhumanity. However, with there being a first time for everything, the first time Myles Garrett circumstantially proved gravity a farce makes the umpteenth time seem just ever so slightly less impressive than the most impressive thing ever.