Writing kind of come naturally to me now, I am not sure if I felt like this way three years ago. So I guess all you would need is experience, time...
Of course a character could be both a protagonist and an antagonist (like in Dr. Jekyll and Mr. Hyde), but unless it's is a deep...
He can't be both the protagonist and antagonist at the same time... However, he could be an evil/demonic protagonist for a good purpose/resolution...
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