"Ha ha ha!" laughed the villain. "My recipe calls for only the finest baby unicorn penguins! Even though eating one will literally cause thirty atomic bombs to go off around the world, I must sate my hunger!"
Sound familiar? How about this?
"It's truly incredible." said the side character in awe. "Now that you've thrown off the shackles of eating any kind of meat, you are clearly the best of us all. Our one true God has granted you the ability to smite all of the redneck gun owners who would do nothing but overthrow society with the desire to eat all that they see because clearly they have no morals or wills of their own outside of an insatiable desire for blood!"
How about this?
Honestly, I hope not. Because if it does you very well might be reading some serious garbage.
Now, before I receive another angry e-mail claiming I am supporting some weird nuclear-penguin eating agenda, let me just say this: this was the first random example of a terrible villain and hero that came to mind. Overly psychotic, blood-thirsty monster and exemplary, pure, perfect, holy hero who could never harm another soul. With that said, do you see the problem with these examples?
In short: these characters aren't even black and white. They're at best white or black in their design. That said: let's talk characters!
What makes a good hero AND villain really interesting is their relatability. While you might be inclined to make a villain truly monstrous or a hero a shining beacon of light, I would discourage you from such writing tropes. They're rarely done right and doing so makes them confusingly evil or unattainably good. Instead, look at it from both sides. Why is the hero good? Why is the villain evil? Where did they really come from that makes them who they are?
While I'm pretty sure I've used this line before, it's still one of my favorites and is definitely worth repeating.
"No one thinks that they're the bad guy."
With that said, consider that from the perspective of the villain. Most real people aren't going to actively make choices that are just outright evil. Example given, eating the one, lone unicorn penguin AND destroying the world via nukes linked to said unicorn penguin seems a liiiiiiiiiiittle out of realistic trains of thought for any given individual. Instead, consider the choices that got them there. Consider where they are coming from but also where are they going. There's a reason antagonists are called antagonists versus fucking-evil-bad-guys. It's because they are working opposite to protagonists. And that doesn't mean evil...just opposed.
But hey, let's apply that same logic to the heroes. Surely you've heard the 'misunderstood villain' shtick before, but what about the fact that the hero doesn't think they're the bad guy either! They're not the bad guy. Right? Riiiiight? There's no way that this guy whose a shit driver and cuts people off in traffic is bad. Or the guy who doesn't tip is bad. How about that hero who kind of hates black people. He's the good guy right? Well...he's the protagonist. And just as the villain isn't necessarily evil, the hero isn't necessarily good.
In fact, they're all just human.
Unless they're aliens.
Then fuck those guys, am I right?
PS: Sorry to all of my alien readers. I love you and couldn't help myself.
So going forward, I would encourage you to consider your heroes and villains both not as tropes, i.e. good and bad, but as people. People working towards opposite ends in opposing ways. People with goals that they want to fulfill for some reason or another. The thief who needs money. The fighter whose been misled. The princess with an addiction. The man with a mission. None of these are necessarily good or bad...it's just how you use them.