What would you do to drive a sub crazy?

Apologies for the belated reply. It depends on the guy and their specific kinks/fetishes. But obviously the easiest and funnest is through tease and denial: pleasing them, edging them, controlling them. I give them a taste of what they want, and then take it away; let them know that it’s there, dangle it in front of their faces, but don’t let them have it; even when I’m pleasing them, I taunt them, reminding them that I control their pleasure, and I can just as easily take it away or punish them. There are few things more frustrating than simply not being able to have something tangibly within one’s grasps.

And to make it even better (or worse, depending on your perspective), I take my time, slowly building up to pleasing them. I toy with them, teasing them with kisses and caresses, leaving their senses on edge and them anxious with anticipation of what’s to come. It is this psychological and physical loss of control and frustration that keeps them begging and subservient.