Question: what beers are not bitter?
Answer: Having said all that, there are several styles that are not bitter: Sours like Lambic, Geuze, Kriek, Berliner Weisse. Very very malty styles like Bock, Doppelbock, Scottish Ales, some Triples, many Quadruples, some Belgian Strong Ales, the beers by Rochefort, Doppio Malto beers from Italy, etc.