I think that for Nietzsche ressentiment is more of a toxic by-product that is generated when traditional aristocratic or virtue-based morality (where "good" equals success, excellence, victory, etc) is inverted into modern morality (where all the things that were previously held as bad like weakness, meekness, victimhood, etc are now "good"). He associated this so-called "slave morality" with Christianity but he also saw it as a coping mechanism that came about as humans learned how to contend with increasingly structured and regimented societies.

In his view this was an obstacle to true human flourishing, and he hoped for some kind of creative renewal where people invented new values that were more authentically life-affirming.

Wikisource has the book online: https://en.wikisource.org/wiki/The_Genealogy_of_Morals

Nietzsche is probably one of the most misinterpreted philosophers out there (I definitely consider him a thinker to "handle with care"), and I'm not necessarily advocating for the correctness of his views. But I think it's interesting to see how previous thinkers have anticipated a lot of our current debates and questions.