We can bank on people acting in self-interest. The nefarious actor will find themselves opposed by millions of others that are not aligned with them, so it would be much more difficult for them to do things. It's like being covered by ants. The average alignment of those ants is the average alignment of humanity.
Yeah, that has worked very well historically, hasn't it. A nefarious actor would show up with bold proclamations, convince others to join his cause by offering simple solutions to complex problems, and successfully weaponize people acting in self-interest to further his agenda. Never happened before.