Physicality comes in many forms.
IMO It's a mindset first and foremost but having the physical attributes like size, strength, arm length and power at point of attack help as well.
The guy who lines up and looks at the QB like he's trying to hurt his family. You know like Alvin Mack in "The Program"
That nastiness that some guys just possess. The ones that either pancake or knock the snot out of you then let you know its only going to get worse.
One thing is certain, either you have it in you or you don't.