He developed an alternate personality that is a lot more screwed up than he is that basically was born due to his trauma of being disowned by his family and locked in a cage for millions of years.
LUCIFER
ARCHANGEL/DEVIL
ALL HE EVER WANTED WAS
TO REUNITE HIS FAMILY
KILLED ROWENA MACLEOD
OVERGROWN CHILD; AZAZEL
PRINCE OF HELL
ALL HE EVER WANTED WAS
TO SAVE HELL FROM HEAVEN
KILLED MARY WINCHESTER
BAT SHIT INSANE