I generally hate NTR with a passion. There's two exceptions. The first I mentioned in my thread about counters to netorare. The other is where the man legitimately earns it.

Please understand, I am saying he truly earns it, he doesn't just "have it coming". You set up any story where something bad happens to someone, and you'll find someone out there who will try to reason that they deserved it. Netorare is a very special hell of jealousy, betrayal and loss, and a person can't earn it because he doesn't see it coming, or because he didn't go all the way with the girl himself, or because he didn't do her often enough, long enough or hard enough.

Ugliness, weakness, and cowardice do not earn a person a place here. I know some of you disagree, and frankly I couldn't care less. I'm not looking for debates about what deserves this. I'm looking for an extreme case where even someone like me will feel a sense of satisfaction seeing him suffer.

In other words, I'm looking for this to happen to bastards who aren't just weak or slow, but who actually DO things so horrible that I almost want him to have it cut off and forced down his throat. One example would be the teacher from the Bokurano manga, who makes a living seducing, training and marketing little girls one after another. Or most men who commit the taking in an NTR. Things like men who take women through force, deception, or other manipulation and enjoy stripping them of their humanity until they're nothing but his toys.

An important part of NTR is that the guy doesn't earn it. In fact, I think part of what makes a series NTR is that the woman places herself in a worse situation as well, and seems to enjoy it. If the guy is scum, then the feelings of having the woman "stolen" don't exist, because instead of becoming an object that can be stolen away, the woman is instead acting like a human being and choosing to leave an unfavorable relationship for a better one.

This signature was recovered from Hades to serve in my rotting armies.

OK, the term netorare simply means that a partner is taken away from their lover, most often sexually (in fact, the "ne"(to sleep) can refer either to the person being your partner in bed or that the taking involved "sleeping with" them). Technically, the man can be a true bastard, though in such cases it's true that one probably wouldn't see it as NTR. So, if it makes you feel any better, you can call it "liberation".
Anyway, it can still have the villain enjoying and feeling secure in a relationship only to have it taken from him. As is sort of shown in Onani Master, even the worst people have good sides, and no one is all bad.
Generally, in most cases, it doesn't matter how evil a man is, having a "partner" who he values in any sense taken from him generally causes the same reaction and the same pain. You cut him, he still bleeds. The only difference is that this is someone you want to see bleed. Particular bonus goes to any case where a man who "took" another man's girl while he watched is forced to watch as the other man "takes" her back.

the only one i can think of off the top of my head is a hentai anime called hypno love

AKA Saimin Gakuen. Don't remember anyone being taken from anyone else. Except for when the hypnotist took a girl's virginity in front of the weak-hearted childhood friend she adored, though that one might not count for various reasons, and I don't remember the kid being bad. The show is good though, and I liked how it turned out.

The boy who's been hypnotizing girls falls in love with a girl for real, then finds out that she had been hypnotized to fall for him. He reacts very badly and tortures her before removing the hypnosis to find out what she really thinks, and she says that at first it was disgusting but after a while she started to actually like him. Rather than having his girl taken from him, he destroyed the only true love he had.

One anime that I recall is called Rensa Byoto. The main character's out for revenge on the doctor who made a "mistake" that cost his father his life, and so becomes a doctor in the hospital said doctor took over. The doctor turns out to have married the young man's old tutor and crush, who fell for him when he saved the hospital from financial ruin. He was living a happy life, but it was based on a lie, since he'd used a friend to siphon all the hospital's finances to him, both causing the financial crisis and giving him the means to "save" the hospital, ultimately allowing him to make the place his own. This is one possibility, a man who's secretly ruthless and cruel, who is able to have a serious romance up until the moment his secret's found out.