There are morality alignment points which changes upon your decisions.
So yes you can make your MC go evil.
I don't think corruption points for LIs necessarily mean turning LIs evil.
To me, "Corruption" just feels like making LIs more open to more sexual/perverse acts/kinks that they wouldn't do (compared to their "Love" points ways.
For example, Mida would get increase in Corruption points if MC convinces her to do threesome with him, her, and Finnay, but increase in Love points if MC rejects Finnay and decides to be with just Mida herself.
Also Bredita's main kink is FemDom with everyone being submissive to her, which increases her Love points, but MC deciding to be dominant i.e. MaleDom will increase her Corruption points.