HEI HUA WANGYE CHAO NAN HONG

Ever since novelist Qiao Xiaoqi changed the ending to her novel, she was cursed to isekai into her own story as the female lead who gets killed by the male lead! When the personality of the male lead, Jun Mojue, grows more and more twisted due to constant persecution, Qiao Xiaoqi tries to stop him from going down this dark path. At first, she just wanted to decrease his darkness percentage so she could go home, but soon she started to have real feelings…

(Souce: Bilibili Comics)

Note: Bilibili Comics originally titled this work "The Malevolent Prince is Hard to Please" (as can still be seen in early chapters), before renaming it "The Dark Prince Is Hard To Please".