In “The Brothers Karamazov”, one of the characters has a “visitation” (might be a dream, might be a hallucination, might be bona fide) by a devil (might be THE Devil).
The vistor says that he CAN’T repent, by definition. He is the Principle of Negation, and were he to renounce his post as the Adversary, then Negation Itself would be negated, and the whole of creation (Earth AND Heaven) would collapse into non-existence.
Or, to quote Tim Curry:
There is a balance to the universe.
The struggle to maintain that balance
is the stuff of legends.
For there can be no good without evil.
No love, without hate.
Life needs death.
Innocence feeds lust.
There can be no heaven without hell.
No light, without… ME!