We've seen Megatron's eyes and circuits or body parts glow purple due to infusing himself with Dark Energon. This kind of glow is very much the same effect displayed by undead Cybertronian raised by Dark Energon. Megatron was on the brink of death after the "Darkness Rising" arc. He survived and was revived by Dark Energon. And we know Dark Energon raises dead transformers as undead. So is it possible that while Megatron retains his mind, will and personality. But he really is already Cybertronian version of vampire/zombie? In most fictions and stories, creatures like vampires possesses greater strength and other physical capabilities than humans. And the causes for humans getting turned into vampires are usually vampire bites or vampire blood. So Dark Energon is like vampire blood, Megatron taking it into himself is like turning himself into an Alpha vamp, and goes on turning others into the undead. Of course he still seems more alive than dead. But since Dark Energon is the Anti-spark, or antimatter to Energon. It doesn't seem likely that Megatron is alive in the Cybertronian sense.