Not even the most famous authors in history write the perfect character.
For your entertainment - and so you know some books considered literary classics and that are also taught in schools can have... execrable characters - I came across a list of:
The 50 Most Hated Characters In Literary History.
Some will surprise you, others will have you nodding in agreement. Most you should know.
The list mixes hated with love-to-hate characters and if you consider closely, you can see the whys and wherfores, understand the motivations and actions of those characters.
It's worth thinking about as Nano approaches. Are your characters 3D, or cardboard cutouts? Have you set up a few mistakes or an epic blunder for them? Is your antagonist evil because you said so, or because of a genuinely held belief?
Or are you going to make it up as you go along and fix it later?