Again, I think the "slave" route is weak mainly because it keeps dancing about the concept rather than committing to it, and yes the art in some places (especially the street and statue island zones) is so bad it is jarring. Tenzin is pretty much a requirement if you are going to do both Korra, air-bending and keep the MC a male. Plus, it is nice to NOT have a teenager as the MC in this game for once.
But the game plays around the slave storyline way too much. It would fit the story and the line much better if Tenzin was a LOT harder on Korra. Most of the beginning of the story arc should have been scrapped or at least shortened considerably, and add in an option for Tenzin to regularly visit and torment Korra as "Amon", stripping her powers away from her and pushing her farther and farther toward breaking. Mixing the sexual acts with Amon instead of just Tenzin with a strong BDSM twist would have also helped. Some public humiliation acts, maybe some degredation, even more cucking her with Asumi could work (say, having Asumi regularly please and pleasure Tenzin and making her admit how much she enjoys it, enjoys a "man" while Korra is bound and gagged in a closet watching, to break her from her romantic potential with her and make her feel even more helpless).
I just feel like Act 4 is just not aggressive enough. This is the one and only time YOU get to be the Dom AND the teacher, you get to be in the role of control over the female character. The MC also has near-total support from the people around him to break Korra....so just fucking DO it. Go full supervillain and break the bitch. Don't be nice, don't be a hero, don't justify it, just fucking DO it and go all in on it. By the end, Korra should be a completely broken and submissive slave of a girl, that exists only be humiliated, used and abused...and then maybe that is how your MC regains being the "Avatar", because she gives it up.