Okay, okay. I'm sure everyone is going to hate me for saying this, but most speculative fiction baddies (i.e., the so-called bad guys) are terrible. Not terrible as in their behavior, but terrible as in their execution being terrible. I am reminded of the sage words, which I will butcher later, by George R. R. Martin. Martin suggests that baddies should feel as if they are the heroes/heroines of their own stories. The same idea is mirrored by the works of F. Paul Wilson, who believes that bad guys really aren't as terrible as we are led to believe. In other words, a baddie isn't someone or something that laughs maniacally, smokes cigarettes in dark rooms or places that aren't well lit, and/or has a funny or weird accent. Instead, a baddie is just like you or me. Don't believe me? Consider this.
Baddies, even when they are the epitome of baddies—think: Stalin, Pol Pot, or even Hitler—don't believe they are the bad guys. In fact, many of them believed they were saving society, the world, the human race, fill in your ultimate (noble) goal here. They just went about doing so in ways that we see as evil, although, again, they didn't see it this way. Instead, they saw their actions as justifiable, a necessary evil to ensure the betterment of mankind, the nation, the world, or whatever.
This, I think, is important to know. When we consider baddies in a different light, it makes them easier to understand and it cuts away those abstract terms like good and evil. Although some would argue that the big baddies—Stalin, Pol Pot, Hitler, etc.—were indeed evil, this might be problematic. Would we consider these individuals evil under different pretenses? Would they be considered heroes/heroines in a different light?
Even the so-called good guys have done some pretty shady shit, in the name of good. Don't believe me. Google the firebombing of Dresden or even the bombing campaigns that took place over the skies of Japan, just before the Japanese were forced into an unconditional surrender.
Goodness and evilness are problematic, to say the least. I recently wrote a Medium article on the issue of moral ambiguity and how moral ambiguity—that is, an unclear distinction between good and evil, right and wrong—is the ruling factor in our lives, and it has been this way for some time. If we take moral ambiguity seriously, we see that the shades of good, evil, right, and wrong, intermingle into a complex moral geography, one in which characters, protagonists or even antagonists, must navigate and resolve their own moral dilemmas within this particularly difficult bit of geography.