Sorry, I didn't think I would recieve a reply. It was a bit of a joke answer in that the churches of all three are "corrupt." Each one of them is comprised of multiple parts which exist in contradiction with each other part, and as each part or faction gains the upper hand against another or completely does away with the other, the church (or any other organisation) as a whole changes character. That's what I think is meant by "corruption," but this is true of any organisation. If all churches are "corrupt" because their different internal parts are always in motion and contradiction, then there is no manga with church which is not corrupt. I chose Risou no Himo Seikatsu and Overlord because they give alot of detail to the inner turmoil of their churches, but also Mynoghra (and Overlord again) because Evil vs. Good objectively exists and therefore a second definition of "corruption" as Evil imposing itself on a church does, too. I haven't read Mynoghra in a long time, I'm not caught up at all (that's why I don't give it a full name like Risou no /.../, I just don't remember it!). But in the early chapters the would-be massacre/ethnic cleansing/genocide of Dark Elves would have been Good because the Dark Elves are Evil and an effort against "corruption" (the second definition) despite it being done merely to sate a character's personal hate for Evil and being organised as an effort of one side the church against another internally ("corruption" by the first definition).