You don't get this in the manga but in the novel you get that Cliff knew what Rizze was doing especially her wrong acts. She in fact was lying about being innocent these supposed coincidences Cliff pieced it together. Keep in mind Cliff is so brainwashed into loving her that he notices all the things she does, but still goes along with her. So Cliff in fact knows that she is behind all the events that took place from the time Edith even fell into the water on the ship. As Rizze was in fact talking to Cliff about the ship & had someone go to the ship. Cliff openly knew but didn't care.
Spoil below if you don't want to see don't go further.
In the end of the novel we see that he was truly obsessed like a stalker mindset with Rizze not so much mind control by Rizze or the system. Though he only see this when he finds true love and he realizes the difference.
He still ain’t shit.
The brainwashing made people trust her unconditionally and assume she's this lovely pure person. Cliff knew what she was really like and was helping cover it up. The system isn't in control and he's still acting like that because he's really just obsessed with her.
Yeah I’m struggling to see him as a villain as well. He’s playing the role he was assigned to play. Never broke away from the home she had over his character. Everything you mentioned about Killion and Edith just forgiving him because he was brainwashed is also part of the reason why the main love story isn’t all that great to me, but that’s a different point.
By the second stage the restrictions were more than half removed he could've stopped reeze, even if he was "obsessed" catering to her wishes and harming his family was his full conscious choice. Just like how killlian chose Edith over reeze he could've found a middle ground of his responsibility and his obsession with her
I understand the desire to punish him but why would you blame the most brainwashed character in the novel and let everyone else off so easy? Like Killion, who also made her suffer a ton we let off with "it's not your fault it's the author's will"?
You may argue that Killion changed but he only changed because Edith oposed him and the author mostly ignored him. While Cliff was under full control and had only incoragement from Rizze?