It isn't until Rex slides along the surface of the rock facing Megatron that he speaks again, EMP grenade held tightly in his fist with a blaster in the other.

Noticing that Megatron is looking directly at him. It's almost as if that armor tenses up, his feet twisting into the ground to get a better grip on it. Just in case he needs to run.

"Never seen one as big as you, before."

In a way, he's kind of impressed. Grevious is stepping up his game.