There were several in the series BIG LOVE. Two that come to mind (with Open Spoilers if you haven’t seen the series):
Sissy Spacek was brought in as a two-faced lobbyist in a long plotline in which she played both sides of the casino gambling industry- simultaneously lobbying to legalize it and to keep it from happening. She was portrayed as ruthless and tough as nails and the entire season built to a showdown twixt her and Bill that just- ended. He confronted her with her double dealing, she threatened him, and- that was it, no payoff. You assumed that such a cunning character, played by an Oscar winner, was going to become the show’s chief villain but… nope.
Another season ends in a silly soap operatic plot with Bill and his family all being kidnapped by a maniacally deranged messianic cult leader, Hollis Green, and his primary wife, Brother Selma. This is a cult in the series that has committed murder and attempted murder and manslaughter throughout the southwest, they have kidnapped innocent children to punish parents they have a beef with, they have branded people (literally, with branding irons) and tortured them in numerous ways, and even Hollis’s brother-in-law and super-rich and no-stranger-to-getting-his-hands-bloody rival cultleader is afraid of them because they’re not just ruthless they are crazy and think their work is by definition divinely sanctioned. These folks don’t play in other words.
So, at the end of the season they’ve kidnapped Bill and several members of his family (wives, kids, parents), imprisoned them in an ostrich pen, and are preparing to execute them when Bill’s mother, Lois, manages to grab a machete and in one whack, as cleanly and smoothly and with as little upper arm force as if it were a light saber, she hacks Hollis’s arm off at the shoulder. His cult, including his crazy wife Brother Selma and his other wives and children, all stand around and watch as the Henrickson clan leaves with far less interference than the von Trapps leave Austria, because it’s decided they can’t both get Hollis to a hospital AND go after them.
Now, in reality, the Greens would likely have mown them all down with machine guns right there, and THEN done whatever needed doing for their patriarch. Since they don’t, you assume there is a major showdown coming between them and Clan Henrickson, especially when you learn later that Hollis died.
Nope, just dropped. Apparently the Green cult was “all they did was mutilate our Chief Prophet and Revelator, an immortal Apostle (which he had claimed) and head of God’s church on Earth, and really, who hasn’t done something bad in their life?” Just dropped. Particularly maddening as Sandy Martin who played Brother Selma was one of the greatest characters on the show.
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Backing up several years, Queer as Folk (the U.S. version) had several of these. One big one that comes to mind:
The character of Emmett, a penniless late 20-something club boy, fell into a romance with an extremely rich old man (probably 70ish) who died a short time into their relationship. The old man left Emmett $10 million in his will- completely unbeknownst to Emmett- and of course Em, who really did love the old man, went on a spending spree and bought expensive gifts for his friends and for himself.
Unfortunately the old man’s estranged family, led by his ex-wife, challenged his will, claiming undue influence and elder abuse and the like, and somehow freeze Emmett’s bank accounts. (Can they even do that in real life?) Emmett retains a lawyer (one of the show’s main characters) and the old man’s family offers him an out of court settlement of $2 million if he will swear under oath he never had a homosexual relationship with the old man. Emmett refuses, gives back the trinkets he has bought and his friends give back the gifts he gave so he can turn them over to his family.
I kept thinking they would pick this plot up eventually or at least mention it again. Emmett’s character, you would think at least, would have an excellent shot at winning any litigation: the old man wasn’t like Anna Nicole’s sugar daddy (though I always thought she deserved money also) but was in clear mind, reasonably healthy (obviously had a heart problem but prior to his fatal heart attack he was mobile and not dependent on oxygen or anything like), and there was no reason at all to think he was mentally ill. If I had a shot at $10 million, it would pretty much dominate my life and conversation, and yet on the show it is never mentioned again.