Megatron was aiming his fusion cannon at StarScream. He was angry, annoyed and fed up of StarScream's betrayals and backstabs for once and decided to act up on it...but then had a change of plans again and decided to grab starscream and hold StarScream to his face

Megatron: "It's either you're lying, or you're stupid!"

StarScream replies in his usual annoying voice, frantic as always

StarScream: "I'm stupid, I'm stupid!!"

Megatron drops StarScream

Megatron: "Good."