Goro is a shokan , who has his own layer. He is a sub-boss.
Kintaro is also a shokan, but has tigrar lineage. He can breath fire, and is the jerk who burnt Kabal. He is a sub-boss.
Shao Kahn is the emperor of outworld who made his debut in Mortal Kombat 2. He is the main boss.
Which is your favorite?