If you want to translate the original 人鱼圣尊 character by character, the first two (Rényú, as transliterated by Google) correspond to "fish people," which is apparently a standard form used to denote "mermaids." The last two characters (shèng and zūn), mean something like "holy" and "respected," and so "saint," in the sense of "respected for holiness" is not a terrible translation.*
For the title "Mermaid Saint" to be idiomatic in English, it would need a definite article, but "the Mermaid Saint," seems fine for expressing the required meaning. On the other hand, "predor" is unknown to the Oxford English Dictionary; it does not mean anything in English. (In a comment, Valorum suggested it might have been meant to be "praetor," which is possible, although there is no holiness aspect of that title; it just means a high elected magistrate, both in its original Latin context as well as occasional usage in English.)
*Although I got the transliterations from Google Translate, I ran the whole reading by Chinese friend, and he confirmed it.