Any respect Starscream might have been beginning to harbor for Megatron by virtue of, well, being Megatron pretty much immediately drops away, and his expression goes cool and flat.

"You lost, and now you wear the enemy's brand?" This Starscream is, admittedly, not as practiced in the art of giving Megatron scathing looks of scorn, but despite that he manages it pretty well. "You might look like him, you even talk like him -- but you are not Megatron."