He is the closest. In a world like Dune that is sufficient, I suppose, if damning with faint praise.
I can't think of anything he did in
Dune that was objectionable, unless you want to count getting drunk on spice beer and calling Jessica a "damn Harkonnen spy". But since that's what he was supposed to think, I can't really blame him for it. At least he didn't try to kill her, like Gurney nearly did.
Duncan wasn't himself throughout most of
Dune Messiah, as his true memories hadn't been awakened yet. I don't want to blame Duncan for objectionable actions taken by his ghola persona, Hayt.
Children of Dune, as mentioned, is problematic. It just seems wrong for him to have married Alia, and then his attempts to redeem his honor... I'm going to have to reread that, to see if I'm remembering it correctly.
God Emperor of Dune... yikes. Yes, it's understandable that he's confused, upset, grieving, and bewildered to suddenly wake up to a bizarre world that's 3000 years later, when everyone he knew is dead and yet he feels a compulsion to serve Leto II just because he's an Atreides. People have criticized him in this novel because of his disapproval of same-sex relationships among the Fish Speakers. Was that really Duncan's attitude, or was Frank Herbert using Duncan to express his own disapproval?
Heretics' Duncan is a teenager and most of his actions aren't his own - he's somewhat controlled by the Bene Gesserit (he states that he has no intention of mating with Sheeana as the BG want), and the Honored Matres attempt to control him as well.
And then in Chapterhouse... I still don't understand parts of that novel, even with the number of times I've read and discussed it on Dune forums. Being held prisoner in a no-ship for however many years, constantly under Bene Gesserit observation, would be a horrible experience in my view.
The most disturbing thing about Chapterhouse is the incest angle involving Teg. That's one of the primary reasons why the Bene Gesserit will never be part of the "good guys".