Envy? I don't know about that, but this is Rodimus. He's been aimless for the better half of the last few centuries, and suddenly Megatron is back in his life. You're either competition, something he's going to meticulously compare himself to looking for his own shortcomings, or both.

[ Drift makes a noise that's almost pained as it was tired out ] Either way what he thinks is that he lost.