거짓말쟁이 or 가식쟁이 가식쟁이 is more like someone who is pretentious. ex) Sam은 진짜 가식적이야 = Sam is really pretentious.(hypocritical)

"liar" is "거짓말쟁이" and "fake" is "가짜" in Korean. For pronunciation, "거짓말쟁이" is "geo jit mal jaeg ee" and "가짜" is "ga jja". Hope this is helpful.