It honestly annoys Sentinel how easily his forearm breaks in Megatron's grip. Like it's made out of cardboard - he'd thought it would've lasted longer. Evidently not.

Stubborn as ever, Sentinel refuses to admit to himself he's losing badly. He braces off his feet and pushes himself forward into Megatron, hoping to knock him onto his ass. The broken joint in his knee twists and shrieks with the added strain.

Double delightful.