Disbelief after Belief
Indeed, those who disbelieve after having believed, then increase in disbelief, their repentance will never be accepted, and they are truly lost.
3:90Lo! those who disbelieve after their (profession of) belief, and afterward grow violent in disbelief: their repentance will not be accepted. And such are those who are astray.
16:106Whoso disbelieveth in Allah after his belief - save him who is forced thereto and whose heart is still content with the Faith - but whoso findeth ease in disbelief: On them is wrath from Allah. Theirs will be an awful doom.