Slannesh is one of the dark chaos god in the Warhammer 40 k and Warhammer fantasy series. The concept of the Slannesh is all things in excess and obsession. From gluttony to lust to megalomania, worshippers and follower of the dark god Slannesh will indulge ever more debauchery and pleasure beyond imaginable. Every act from the previous to the next and the future becomes ever more extreme and intense to achieve the greater highs.
In short, although a fictional character from a series that has completely nothing to do with this series, has a lot to do with NTR. The concept of Slannest demands that the corrupted descent ever more into lust and desire, that spiral into an unending hunger to demand more twisted debauchery. For example in NTR, once the main girl is corrupted, she slowly start with liking being groped, touch and feel up on. Then to kisses, tongue and licking. Oral sex to full on sex. Anal. But eventually sex itself is not enough. Now there is kinks like nipple pulling with pliers and anal toy while banging. Mouth plug. Butt plug. Nipple plug. Then there is drug, piercing, toys, gang bang and line up. Other extremes are banging in MC bed, or while MC sleeps in front of MC. Literally behind MC. while he is turn distracted. Banging in front of MC while MC tied up, capture or kidnaped. Confessing to MC all the evil ish thing imaginable like small pp to liking his enemy, rival or boss more, being cock hungry whore. Every insult in the degenerate in evil book.
So I would have to disagree with you. MC should not get a good ending. Unless he gets corrupted himself and steals the pink girl then sure. But then he has a small pp and is a good guy which goes against NTR concepts sooo nah.? Unless he take some kind of super enhance drug or meet a magical old man who bless his pp giga chad size then sure. Yeah?