When I used the mod (essential for this game, sadly), I found that if you just consistently choose the red option, regardless of the corruption factor, you end up with the most corrupted Katie.
Now, I'm not saying that's what I would have wanted, but I've gathered 3Diddly was mostly directed by his patrons rather than an inner muse, so he basically just drove the story in one way: total depravity. Choosing any other option generally left you with "game over" (purity), no matter how far down the corruption path Katie has already progressed.
Weird, but effectively just ending up a kinetic novel rather than a branching one.