He's frustrated. Frustrated with Bumblebee -irritated with himself for letting Bumblebee get hurt in the process. Optimus couldn't bear to see Bumblebee all broken up and beaten. Why didn't Bumblebee listen?

"I told you to fall back." He scolds, optics scanning Bumblebee for any more injuries. He sighs. Optimus's not sure if he enjoys Bumblebee's stubborness that much.

He's worried for Bumblebee but he tries not to show it. He doesn't want Bumblebee getting hurt time and time again because of him. Bumblebee is his sparkmate--his everything.