Loop kara Nukedasenai Akuyaku Reijou wa, Akiramete Sukikatte Ikiru Koto ni Kimemashita

Selene Vixent has died nine times. In every life, she's been betrayed by her fiancé, abused by her noble family, and laid low by an untimely end all because she was unable to awaken the power of Sun, a so-called protective gift passed down in her family. Yet Selene is determined to escape this cursed time loop and, after her ninth demise, abandons any further attempts to be a good girl. She awakens to the power of Shadow—seen as an ominous portent of misfortune—and fully embraces her new life as a villainess. But Selene's dark path is about to take another strange turn when Dier Veldt, the former crown prince, reveals that he knows all about her time loop. He even offers his help, but under one condition: she must kill him in exchange. With her newfound villainy, can Selene break free of this endless time loop once and for all?

(Source: J-Novel Club)