That was indeed enough, and even if he lingered for a moment longer over the head of the spike, tempted to simply (and quite literally) overload Optimus with several overloads, the point wouldn't exactly be the same.

Maybe he'd have a chance or two later.

With that thought, Megatron snapped away, barely keeping from grimacing to exorcise some of the charge still trapped, flickering between tongue and teeth and skipping around. Instead he just carefully ran his tongue along the inside of his mouth while stroking Optimus' thighs, optics glowing deeply as he surveyed his shaking Prime.

Give Optimus a few kliks to wind down, disperse some of the charge, and then move on. It wasn't as if it wasn't pleasant to see Optimus right at the cusp of overload, neck strained, his jaw working around the gag... Megatron smirked as his optics flickered slightly dimmer as he surveyed the result of what he'd done.

Because why not enjoy it? He'd have less chance to when he went further down before actually, ahem, paying full attention to Optimus' valve. It would also give his self-repair some time at the sensors and thin metal in his mouth, since he'd been risking real damage.