Ch.3 Possible discontinued because it didn't win a Naver webtoon contest.
Skimmed through til ch.4.1 RAW https://loveheaven.net/manga-fukushuu-o-koinegau-saikyou-yuusha-wa-yami-no-chikara-de-senmetsu-musou-suru-raw.html
So That's How, The Saintess Became The Devil Of Revenge