Correção de "He's a really good villain''

He's a really good villain.

Essa frase está correta?
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Avatar do usuário PPAULO 39185 6 32 684
He is (pretty) good at playing a villain (or bad guy).
He is brilliant at playing villains, he performs in such a convincing way that he himself might believe he is a villain!

A good villain would perhaps be one that gives children candies as a treat, then get it back! Or perhaps one that helps children to cross the street, but it´s wicked towards the superheroes or good guys!
Nessa frase, há necessidade do "a". Essa é minha dúvida. Perdão não ter especificado desde de o início.
Avatar do usuário PPAULO 39185 6 32 684
Back to the crux (the initial sentence) and to cover all bases here:
Either "He's a really good villain." or "He's really a good villain." wouldn´t be likely (or natural at first glance.)

He is good at playing a villain. AND
He is good at playing villains.
Would be possible sentences to convey the idea.