The Rambam speaks of deviants who anger Hashem by their behavior. His definition of deviant refers to those individuals who do not accept the basic principles of the Torah.
Those who question such basic ideas as the Torah coming from Sinai and every letter of the Torah was given by G-d to Moshe. They must believe in prophecy and Olam Haba and תחיית המתים, the resurrection of the dead. One who denies G-d, has the doors of Teshuva closed to him.
Such a denier was Pharoah who constantly questioned Hashem's existence. The Ramban says that after the first five plagues, Hashem took away his free will and the second five plagues were given against his will.
There is always place for Teshuva but if we stray too far, it becomes a little more difficult to come back.