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Besides Shoot the Shaggy Dog you can also look at All for Nothing and Nice Job Breaking It, Hero.
"Shaggy Dog" Story is the proper trope for long, involved story where the protagonist utterly fails at their original goal. Shoot the Shaggy Dog is a specific subtrope where, not only do the protagonists accomplish nothing, but they die horribly on top of it.
Based on your description, The Boss of It All would definitely be a "Shaggy Dog" Story. The other two might be Shoot the Shaggy Dog, or they might be a regular Shaggy Dog Story, since it's a supporting character dying rather than the main character.
Edited by MetaFour
Usually in a story the main protagonist (MP) has to fulfill a certain quest, he wants to "obtain an elixir", as this is sometimes called. So MP goes on his quest, gets the elixir and everything is fine.
In the trope I am looking for, the story goes like this: MP goes on his quest, gets the elixir and everything is fine. Then something happens, and MP deliberately destroys the elixir - not because that was the intention all along, but because of a spontaneous emotional outburst and for some utterly petty, senseless reason. With this move MP has just the achieved the complete opposite of his quest. All of MP's previous efforts have become a waste. This twist ending comes out of nowhere and is not a done for comedic effect. It is more like a very specific variant of the Shoot the Shaggy Dog ending.
I have three films as examples (ending spoilers ahead):
The Boss Of It All (2006, directed by Lars von Trier): Ravn, the boss of a software company, wants to sell it. MP is Kristoffer, hired by Ravn to help brokering the deal and given authority over the company. (It makes some more sense in context.) Kristoffer finds out that the deal would be unethical (among other things, all the employees would be laid off), so he looks for a way to prevent it. In the end Kristoffer does manage to change Ravn's mind: he doesn't want to sell anymore. But then the potential buyer makes a move that is completely unrelated to business and impresses Kristoffer, who still has authority, so much that he signs the sale contract anyway.
The Circle (2005, directed by Yuri Zeltser): There is a hit contract out for Rick, the husband of Jay, our MP. She wants to save him and succeeds, the contract is called off. So Jay goes home to Rick, where they get into an argument and he annoys her so much that she just shoots him.
Moh Maya Money (2016, directed by Munish Bhardwaj): Aman is in deep trouble with the local mob and needs a lot of money to pay them off, otherwise they will kill him. He tries to fake his own death and his wife Divya, who is MP, is supposed to collect the money from his life insurance. At the end she gets the money and meets with Aman. He makes a move that angers her so much that she shoots him.
Edited by meekee7