Misplaced Retribution

Some retaliation exceeds what's being retaliated to in its severity. But some retaliation isn't even along the same line; it's directed at those who can't reasonably be blamed for what you're retaliating for, except according to exceedingly shaky justifications. Whether it is worse than what is retaliated to or milder, the point remains that it is still indefensibly directed at the wrong targets.

Closely related to Misblamed, and a Sister Trope to Revenge by Proxy and Sins of Our Fathers. Often overlaps with Revenge Before Reason. It's one of the many ways in which a Cycle of Revenge can get ugly. Avenging the Villain is also related, since The Hero (or whoever killed the villain) is usually either blameless or justified. Can often result in a character having an Unknown Rival.

Truth in Television, of course. From a psychoanalytic point of view, this is called displacement, and occurs when someone who feels under attack emotionally retaliates against someone who is a better victim than the aggressor - for some reason, it is more viable to emotionally attack this new target than the aggressor.

Anime and Manga

 * In The Breaker Manhwa, a great deal of characters are after Han Chun Wo, also known as Goomoonryong, because he killed their master or performed some other dishonorable thing upon their martial arts school. He is a complete and utter Badass upon which they have no hope of carrying out their revenge. Therefore, they prefer to target his student, Yi Shioon, which becomes particularly unfair and messed up in The Breaker: New Waves when Shioon.
 * This is played with in Axis Powers Hetalia. Canada is frequently the target of this because he looks almost identical to his brother America, though the countries that are pissed at America wouldn't harm Canada if they knew the difference. That he's very soft spoken means he rarely is able to stop the abuse or convince the other countries (rightfully angry at America) from beating up on him.
 * This is part of the reason why Master of Martial Hearts has one of the worst endings to an anime ever..
 * A particularly bad example in the case of the anime-exclusive villain Valgaav from Slayers; he was subservient to Gaav, one of the world's five Dark Lords, and he goes on an all-out vendetta against Lina and her comrades for killing him. Problem? Another Dark Lord, Phibrizo, killed Gaav, whereas it took a massive effort for Lina and co. to stand against him.
 * Sasuke Uchiha of Naruto is aiming for this, which really shouldn't be a surprise, considering he's a master of Revenge That Surpasses Any Basic Reasoning.
 * This trope drives the entire plot of Yu-Gi-Oh! R. Tenma's anger at Yugi stems from his belief that Yugi killed his adoptive father, Pegasus - which Yugi had nothing to do with; Tenma had tried to shake down Pegasus' butler Croquet for information on the killer's identity, and because Croquet didn't know, he simply said Yugi had "defeated him" (which was true, although the actual killer was Dark Bakura). Even when Tenma's brother tells him his revenge plot is based on a lie, Tenma insists that "the reason Pegasus got killed is because Yugi won against him". Naturally, Yugi wouldn't have had to do that if Pegasus hadn't used kidnapping and extortion in his mad plot to resurrect his dead wife. It is implied, however, that Tenma's anger is due at least in part from the corruption of the Wicked Gods he Duels with.

Comic Books

 * One Green Lantern story's antagonist was the Aerialist, who was under the delusion that someone at Ferris Aircraft had murdered his beloved (death was in fact a freak accident) and therefore sought revenge against the company. Notable for being one of the few times Hal Jordan thought the Insanity Defense would actually work, even citing the M'Naughten guideline.
 * The tragic story of Astrid Arkham, aka the Arkham Knight, and her misplaced desire for revenge against Batman, has roots that can be traced back to the day she was born. Her mother Ingrid - wife of Arkham Asylum’s head psychiatrist, Jeremiah Arkham - was one of the facility’s most generous, compassionate, and competent doctors. She never believed any of the inmates were irredeemable monsters, a view most Gotham citizens had.  Her approach towards the needs of the inmates was reciprocated a great deal;  even the Joker respected her. As fate would have it, she was pregnant when a riot in Arkham was started by a mass-transfer of new inmates, and the stress caused her to go into labour prematurely. As Batman dealt with the rioters,  several of the older inmates - including the Joker, Poison Ivy, Harley Quinn, Clayface, and Solomon Grundy - tried to protect Ingrid and help deliver her baby. While their efforts in doing the latter succeeded,  one of the rioters took one of Batman’s discarded batarangs and hurled it at the doctor, impaling her in the neck and killing her. Whatever reason he had will never be known, as he was killed quickly by the enraged Grundy. At very least, her daughter Astrid was safe - for now. Jeremiah tried to raise his daughter the best he could, often using his office in Arkham as a makeshift daycare. Astrid was a lonely, withdrawn child, and with no friends her own age, due to being homeschooled, started to develop friendships with the inmates. Her view of Batman was thus skewed by their opinion of the hero, and she started to develop a grudge, seeing him as a sort of demon who had hurt her friends. Finally, she found a surveillance video of her mother’s death; the weapon used - but the killer himself obscured - all but validating her suspicions that Batman was a killer and her mother was a victim. Swearing revenge - misguided as it was - she donned the costume of  the Arkham Knight; a very recent newcomer to Batman’s rogues gallery, it remains to be seen just how far she’ll pursue her goal.
 * During the Dark Reign, the Hood used his powers to resurrect the 17 original victims of the Scourge of the Underworld to use as an assassin squad against The Punisher. As incentive, he told them Scourge had actually been the Punisher in disguise. Exactly how many believed this is debatable, but most complied, as he gave them another incentive - the spell he used to restore them to life only lasted 30 days, unless he extended it.
 * In G.I. Joe, this played an important part of the Baroness' origin. Originally the daughter of very wealthy aristocrats named Anastasia Cisarovna, she and her brother often used their wealth and social status for philanthropic ventures; of these involved delivering medical supplies to Saigon during the Vietnam war the same time a certain soldier was deployed there, the one who would eventually join G.I. Joe with the name Snake Eyes. . It turned out their contacts were actually members of the Vietnamese black market and intended to fence the supplies; Anastasia's brother had the misfortune of catching them in the act, and was gunned down in cold blood. Snake Eyes appeared (too late to save the victims, sadly) and killed the black marketeers. Anastasia heard the gunshots from outside, rushed in, and fear, grief, and shock quickly turned to rage, causing her to blame the wrong person - as in, Snake Eyes - sending her spiraling into her Start of Darkness
 * The Punisher. Just the Punisher, really, every last criminal who was even remotely responsible for his family's murder is long dead - as he went after them first - and his one man war against criminals like them is his way of focusing the rage it has caused him. Indeed, it has been highly implied that his true goal now is to perish himself, hopefully taking out as many of them as he can before they take him out.

Film

 * This is Two-Face's deal in The Dark Knight. Rather than the Joker who actually orchestrated his tragedy, he goes after everyone who was involved in the events, no matter how weakly or by how many degrees of separation, even to the point of threatening Gordon's son.
 * In Star Trek: Nemesis, Shinzon directs his hatred of the Romulans towards Earth for reasons which only make sense to the screenwriter. It's never even explained what bizarre line of reasoning led to him wanting to destroy Earth and not, you know, Romulus.
 * Friday the 13th is all about this. Even in the first movie, Ms. Vorhees' motives revolve around revenge against people who are already dead. Jason himself is no better, his rage taken out on horny teenagers who simply remind him of the neglectful counselors.

Literature

 * In Harry Potter, Severus Snape took out his hatred for James Potter on his son Harry, usually being stricter towards his actions then any other student.

Live Action TV

 * In a mid 90's episode of Grange Hill a guy and a girl try to escape from a fire by climbing out of a window. She slips, falls to her death, her boyfriend blames the guy who was with her and spends the rest of the season stalking and harassing him. He eventually stops and apologizes (possibly since everyone was against his vendetta).
 * In Law & Order: UK, is killed in a drive-by by a young man looking for revenge on the police for botching the murder investigation of his brother, a screw-up he believed was racially-motivated. Problem is, not only was, not a bigot, he had nothing to do with the case (and probably would've been steaming mad about it). What's worse, the killer had an idea of actually pulled the trigger (a local drug dealer who may have been lying to gain street cred)--why not go after him or one of the cops who DID botch the case?
 * The Mothership version of this case had a similar misguided attack, but there, the perp was much younger (14) and the victim survived with an injured arm.
 * Speaking of Law & Order, you can also count Jack McCoy's zealous prosecution of a drunk driver who killed three people. Reprehensible, certainly, and fully deserving of a harsh prison term. But it soon becomes obvious that his actions are motivated by the fact that the drunk driver who killed his lover Clare received a light sentence.
 * Cold Case: A young boy is horribly abused in a group home. So when he grows up, does he track down those who abused him and those who let it happen? No. Instead, he selects completely innocent boys who bear only the vaguest resemblance to his former tormentors and kills them, putting them through the same abuse he suffered.

Theatre

 * Romeo and Juliet is built on this Trope. Whatever incident caused the feud between the Montagues and Capulets isn't even referred to, and it seems likely none of the members know or care because they like having someone they can hate for no reason.

Video Games

 * In Ar tonelico II: Melody of Metafalica, Luca for the longest time holds Lady Cloche responsible for the death of her younger sister. Cloche could not realistically have been responsible for that, considering she was only six or seven years old at the time and even though she's the head of state now, she has always been a puppet ruler who never made any real decisions.
 * Mortal Kombat 11; the older version of Kano tells Kabal that his future self is a cyborg due to being marred in a brutal fight (true) and also tells him the fight will occur with Sonya - that part is a lie, told as "motivation" for him to help them. Oddly, it also makes him rather eager to fight her in the Fight Clubbing chapter.

Western Animation
""That was the wrong guy but... that's okay! I think everyone gets the point!""
 * In the Invader Zim episode "Battle of the Planets", Tallest Purple orders someone Thrown Out the Airlock for not remembering Zim ruining Operation Impending Doom I. His response afterward: