The Rambam states that a ba’al teshuvah [literally, ‘mater of return’, [referring to one who left (or was never on) God’s path and then returned to doing His Will]… is beloved and favored by the Creator, and it is as if he never sinned.
…he tasted the taste of sin, and then left it behind and overcame his evil inclination. Chazal tell us that in the place where ba’alei teshuvah stand, complete tzaddikim [completely righteous people] cannot stand. In other words, ba’alei teshuvah are even greater than those who never sinned, because they have a tougher battle to fight against their evil inclination.
…The holy genius Rabbi Avraham Azulai writes that the reason a ba’al teshuvah is superior to a complete tzaddik is that the light is given off when he performs the mitzvah of teshuvah is able to repair all the damage done to the celestial light by his intentional sins.
These sins, which have been transformed into mitzvot, now become a source of great illumination. Even complete tzaddikim cannot perform such mitzvot.