Miss Bingley from Pride & Prejudice is a decent and reasonably subtle version of this. She isn't always played subtly. But Austen herself maintains that Miss Bingley never entirely crosses the line into crass insolence--though she does get close and brings on her own dissatisfaction.
This archetype of jealous, spiteful ex-significant other can be absolutely hilarious. My favorite example occurs in His Favorite. In Volume 5, the not-so-mean girls (they will defend Sato & Yoshida even while competing with Yoshida) compete for Sato. They decided that the winner of a marathon will get a free date with him--without consulting him, by the way.
In the meantime, the twin brother-sister artists chase around after the fighting girls, trying to record their emotions on paper.
Slapstick meets irony--totally funny.
On the other hand, the archetype of the ex and its trope of eternal punishment can get irritating. If the jerky ex is actually able to get between the lovers, I lose interest (and yes, I lost interest in Rachel and Ross early on). If the jerky ex is able to make other people uncomfortable and anxious, I get mad. If it goes on too long, I cease to care. I read for the couple, how they work things out, not for how miserable someone else can make them.
I enjoy a good "evil stepsisters sent rolling down the hill in the barrel of nails" ending (yes, that is the original end to Cinderella) as much as the next person. But even there, I find it tiresome if the comeuppance becomes too deliberately "yah yah yah, we're better than youuuu."Besides, let's face it--in real life, sometimes the jerk just strolls away. The princes in Into the Woods move on when their wives disappear/die. Eh, whatever.
There is a difference between Miss Bingley suffering from an excess of human nature and an ex who is unrealistically destroyed--destroyed!--at the end of a book or movie. In comparison, a number of manga resolve with the ex being befriended rather than destroyed. Eventually, the ex becomes a defender of the main couple. Because, in the end, the couple runs the main narrative.
Unfortunately, a great many romances are almost as obsessed with the ex as they are with the main couple. One begins to wonder, Who exactly is the protagonist here? and then Why do I care?
After rereading His Favorite, Volume 5, I determined that the difference between an ex handled well and an ex handled badly is that degree of obsession. A romance that depends on the horrible ex to bring the couple together leaves me cold--and ultimately, uninterested.
Writers: Unless you want your villain to take center stage, leave the villain alone.
