HipHop wise Buckwild from DITC and Easy Mo Bee, J Dilla may be but i dont think he is really underated.. if u just dont know him u probably dont listen hip hop and if u do and u know know about Dilla then "shame on you"(game of thrones)
I really do think it has to be Focus... Check out the dude resume. Recently I did an interview with him on my podcast Beats Grind & Life. He was already my favorite producer, but I found out how amazing he really is. You guys should check it out. You too might have a new favorite producer.