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I usually have a hard time answering questions like this. For me, art is art; I don't really care if the artist in question pays or paid taxes to the same government as I do.
That said, I guess that either Zé Ramalho or Raul Seixas would be good bets. Other better known artists are a bit more divisive, or stuff that you'd only hear if you're into a specific style (often regional).
Another possibility would be literature, more specifically Machado de Assis. Because even people who hate him (due to his pedantic writing style - the guy is from late 1800s, but harder to parse than Shakespeare) usually admit that he's good.