If you've ever read James Scott Bell's Plot & Structure (which I recommend you do!) you may have come across this question. Getting to know your antagonist--finding qualities that you not only adore but respect--can help you understand your antagonist more and see him as more than a villain with a villainous top hat. Your antagonist is a living, breathing, person that doesn't only exist to create barriers for the hero. He has massive stakes in your story that may have bigger consequences than your protagonists! 

Would you antagonist refuse to pursue the hero if he had to destroy a pet cemetery in the process? Perhaps your antagonist hates modern weapons with a passion and only uses spears (think No Country for Old Men). Maybe this character is extremely spiritual and only does battle using words and manipulation. Maybe he is well liked in his community, so he only uses goons to do his dirty work? There are millions of possibilities here. Finding out what your antagonist wouldn't do under any circumstances humanizes and empathizes him. It makes him seem that much more real and all the more dangerous.

Is there a way for your antagonist to avoid any dealings at all with the hero? Is there a way for him to avoid being the antagonist? Just like how your protagonist must be locked in this situation, the antagonist must be locked in too. Maybe he is forced to stand as a bulwark against the hero because of blackmail. Perhaps his daughter is in the hands of a higher power, a greater evil. Or, maybe he's just plain old obsessive. Whatever your reasoning, make sure your antagonist has one. Your antagonist shouldn't be able to just pack up and leave town--there should be stakes. Clear reasons as to why he's vehemently against your protagonist winning.

Those are the most important questions that help me unravel my antagonists! Have I missed anything? What questions do you use to flesh out your antagonists? Let me know in the comments!