Yami Ochi Seijo wa Senka de Mau

Alicia has been protecting her kingdom as a saint. One day, Alicia is framed by her fiancé, the prince, for cheating on him- She is falsely accused, imprisoned, and publicly executed. Alicia despairs of the people's malice and makes one last wish, which is for this kingdom to perish. However, Alicia, who was supposed to have been executed, is brought back to life by the Demon King who was at war. Now, in addition to the power of a saint, she also possesses dark magic in her body. With this, she can kill everyone in the royal army. This is a revenge story about a saint resurrected from her scaffold and teaming up with the Demon King to destroy the kingdom. (Source: KADOKAWA, translated)