Sunny<>Cassie

I've reached chapter 520 and read some spoilers here in Reddit that says Cassie still Manipulating Sunny and Sunny still didn't kill her, disappointing MC, considering dropping this, If it was Zhou Fan from Demonic Emperor, he would have decapitated Cassie already in forgotten Shore

Btw any recommendations to a novel like Reverend insanity where the MC is ruthless, cunning and strong?