He looks a little surprised to hear that. Well, more than just a little. That really isn't the best example – he turned them into much worse than simply a force to be reckoned with and he's all too aware of it – but what he says after that gives him pause, makes an unreadable expression settle on his face. Unreadable mainly because Megatron's face hasn't had cause to look touched for a very long time, and the mechanisms that govern his facial expressions don't really know what to do about it.

That almost means more coming from Bumblebee than from Optimus – this faith seems harder-earned. Optimus has always wanted to believe in his capacity to not be a fucking supervillain, and that has always seemed kind of foolish to Megatron, even now that he is actively trying to make a better go of it. But hearing that Bumblebee believes in him, this Autobot with no reason not to doubt him as much as any of the rest of them... he wants Bumblebee to be right.

"... Thank you," he says, feeling sort of ridiculous.