This question sounds silly but Megatron would go to extreme lengths to beat the Autobots. He would use other species as allies but first he would control them with nanobot technology so that there'd be no treachery or blunders. Angels and demons would be beyond his control, though. Other robots would be good cannon fodder. Organic aliens would be good labourers and factory workers. Some magic users would be controllable while others wouldn't. I'm including people with super-powers in that category. Many super-beings are impossible, though. For example, those like Hulk are too powerful and would explode if they were ever created. This includes supers with energy beams like Cyclops, Havoc and Captain Marvel. Those like Flash are too fast and would be vaporised as soon as they went hypersonic. Iron Man would die after his first major blow because his organs would be smashed against his skeleton.
Bear in mind that Megatron would be unable to recruit most super-beings because he is no match for the litigation of major ownership companies.