Is he possibly the ML ? I know for sure that I hate the original novel ML. He used the princess and even regifted something so precious to her. I wouldn't have minded if he broke off the engagement with her since love can't be forced but he used her fully and then claims to love someone else and even gifts her his ex-fiancée's gifts. Absolute garbage.
Also the saintess is shit. It seems like the original heroine is nice so at least no cliché bitchy heroine