This isn't for people who make single mistakes and pay dearly for them. This is somebody who does EVERYTHING wrong in their time during the story. Usually very entertaining to watch, much like a train wreck in slow motion. 

1) Cersei Lannister (ASOIAF) 

(This largely applies only to the book version of Cersei, since the show makes her more of a valid contestant to the throne. However, in the books, Cersei is quite different.)   


Cersei Lannister is the Queen of the Realm, and at the beginning of the books, is wife to King Robert Baratheon. Their marriage is a testy one, and Cersei orchestrates Robert's death so her firstborn son, Joffrey, can ascend to the throne. Joffrey proves an even worse ruler than her loutish husband, and his short-sighted cruelty and impulsiveness proves a terrible combination. Consequently, Joffrey dies at his wedding (which Cersei blames on her reviled brother Tyrion), leaving her nextborn son, Tommen, to take the throne. Since Tommen is too young to formally ascend, Cersei becomes the informal ruler of the throne as the Queen Regent.  


While we've seen Cersei from other characters' points of view, the fourth book, *A Feast For Crows,* gives us our first perspective of Cersei from her own eyes. And boy howdy, is she a *mess*. Cersei's POV characters are wracked with paranoia (believing that Tyrion and the Tyrells, a rival family married to her son, are in the walls and waiting for her to slip up). Having also lost her cold and distant father, Tywin, Cersei is also driven by a desperate need to upstage her father and prove herself valid after he disregarded her for her whole life due to her being a woman. All the while, Cersei is a raging narcissist who refuses any questioning or critique whatsoever.  


This means that Cersei makes MASSIVE mistakes in her tenure as the Queen Regent. She regularly destroys her family's alliances out of petty spite or a fear they might take any concession as a means to upstage her. She rids herself of her father's trusted councilors the moment they criticize her, and replaces them with stooges and sycophants. In one damning case, she bankrupts the kingdom further by building a new navy... only to entrust the navy to an untrustworthy rogue *because she thought he was sexy*. And, wanting to establish her legacy right off the bat, Cersei makes brash decisions such as allowing the Church to carry arms in exchange for relieving their debt to the crown while they're in the midst of a literal fundamentalist uprising.  
 

After three books where we watch characters like Jon, Tyrion, and Dany deal with the realities and harsh lessons of careful realpolitik, Cersei's entire character arc shows what happens if someone ignored every single one of those lessons. As a result, she undergoes a devastating fall from grace when her instilled leader of the church turns on her with his newfound power and imprisons her due to her sins. Her brown-nosing "allies" leave her to her fate the moment she no longer has power, and her navy ends up becoming a massive loss when her crush absconds with it to become a pirate lord. And to top it off, her washerwoman has been shrinking her clothes! 

2) Jackie Aprile Jr. (The Sopranos)

  
Jackie Aprile Jr. is the son of the former Boss of the DiMeo crime family, Jackie Sr. Jackie Sr. was a respected mafia leader, a renown boss, and considered a high point of the family. Jackie Jr... is not.   


Jackie Jr was familiar with the Mafia, but his father kept him out of the family business and encouraged him to take on a civilian life. After his father's death and at his behest, Jackie goes into medicine at Rutgers University, and strikes up a romantic relationship with the new boss's (and series protagonist, Tony Soprano) daughter, Meadow. This puts him in an EXCELLENT position as either a civilian or an associate to the family, and all he has to do is sit back and focus on his life. However, Jackie Jr considers the Mafia to be his birthright, and effectively forces himself into the DiMeo family.   


Tony doesn't want Jackie Jr in the family, partially out of respect for Jackie Sr, and partially because Jackie Jr is a complete and utter liability. He shows a lack of foresight, is too dumb to consider anything beyond the best possible scenario for his schemes (leading to him regularly getting excess attention and his crew injured), and thinks he's more important than he actually is. He regularly invokes his father to the point where it becomes a catchphrase, despite the fact that his father's reputation only goes so far when he keeps poking the bear.   


Still, Jackie can't leave well enough alone, and keeps acting like an established mobster despite not making his bones. He flunks out of Rutgers because he keeps skipping classes, and he ruins his relationship with Meadow AND Tony when he gets caught separately by the two of them cheating on her. Tony informs him that he's done with his shit. Jackie decides he's not done, and tries to pull a hail mary to get back in the family's graces by copying one of Tony's moves from his early years: robbing a Mafia card game. Naturally, this goes terribly wrong, and Jackie kills a Mafia associate and shoots a Made Man, making him a dead man walking. After pitifully begging for another chance from Tony, Jackie gets unceremoniously shot when hiding in a Jersey slum.   


Jackie Jr. is remembered for being one of the dumbest characters in a show with no shortage of them, and the thing that separates him from the rest of them is just how badly he fumbled his hand. He had basically everything in life handed to him, and he could have been a success if he just stayed his course. Instead, he wound up dead in a snowbank, all because he REALLY wanted to be a gangster, but refused to learn any of the lessons he needed to learn for it.  

3) Twitch (Holes/Stanley Yelnats' Survival Guide to Camp Green Lake) 

This is admittedly a pretty out-there example, but the popular children's novel *Holes* had a companion guide where the protagonist, Stanley Yelnats, tells kids going to Camp Green Lake how to survive there like he did. He also details his experiences and stories with his various bunk mates at the juvenile detention facility.  


Twitch, a teenager imprisoned for grand theft auto, has a pretty sparse role in the original novel (mostly serving as Zero's replacement to the tent before Stanley runs off to find Zero in the desert). The Survival Guide goes more in-depth about his role at the camp, and Stanley tells us in no uncertain terms that Twitch was an example of what *not* to do at Camp Green Lake.    


From the beginning, Twitch was an obtrusive and over-talkative inmate. Stanley details every single rule Twitch broke on his first day alone, including...

* Takling over everyone (Everyone's tired as hell, and Camp Green Lake very much values their pecking order)
* Going through other camper's things (Those are the only ties those campers have to their homes, and touching them is a great way to get your ass beat.)
* Mouthing off to Mr. Sir (Mr. Sir is incredibly sadistic, and deliberately encourages Twitch to over-exert himself on the first day he digs his hole, wildly considered to be the toughest day) 
* Drinks all his water in one go (You're encouraged to conserve your canteen as much as possible throughout the day, since the truck gets in late and refills aren't guaranteed) 
* Asks his neighbors for their water (Nobody's giving you what you wasted)  



Stanley even half-joking comments that the last thing he heard before he ran from Camp Green Lake was Twitch telling everyone to look at the cool lizard he found with yellow spots. (If you get bit by one of those, nothing will save you.) 

[Loved Trope] This character is a living example of what NOT to do in this setting.