Bellatrix Lestrange briefly tortured Neville with the Cruciatus Curse, both to try to make Harry hand over the prophecy and to see how long Neville held out before "cracking" like his parents.
Due to his humiliation in the Triwizard Tournament, Cedric eventually becomes a Death Eater and kills Neville Longbottom. Due to Neville's death, the final Horcrux Nagini was never destroyed, and as a result Voldemort is never defeated, kills Harry and takes over the Wizarding World.
Mad-Eye hand-picks Neville to watch as he tortures a bug with the Cruciatus curse, and of course, this traumatizes Neville. Crouch obviously knew what he was doing when he forced Neville into this position. This was Crouch's way of torturing Neville.
This interaction takes place because Neville is visibly upset after witnessing the demonstration of the Cruciatus Curse, which was used to torture his parents into insanity by Death Eaters [2].
He was setting things up so that he could give the book to Neville, which Neville could give to Harry, so that Harry could win the underwater task. Another explanation could be that he despised Neville's parents and perhaps felt sorry for Neville for having such weak parents.
NEW - Every Single Detail Of What Happened To The Longbottoms
Was Neville the chosen one?
The prophecy is mentioned throughout the series, however, it never exclusively mentions that Harry is The Chosen One and suggests Neville was another option. However, one theory explains why, in reality, this wasn't possible.
In the film version, Barty Crouch Jr. has the habit of licking his lips when threatened, in a snake-like way, to which he occasionally shows while under the disguise of Alastor Moody. This action led to him giving himself away to his father following the second task of the Triwizard Tournament.
For example, despite being furious with Bellatrix Lestrange for her murder of his godfather in 1996, Harry Potter was only able to cause her a brief moment of pain with the Cruciatus Curse because he used it out of "righteous anger", though he was still able to knock her off of her feet with it.
Voldemort isn't even the one who used the cruiatus curse to torture the Longbottoms. It was Bellatrix, Rodolphus, Rabastan, and Barty Crouch Jr. Why did the 4 Death Eaters used the cruciatus curse on the Longbottoms rather than the killing curse? Well it's because they want to make the Longbottoms suffer.
Lucius Malfoy was one of the many Death Eaters who denied their allegiance to Voldemort after the end of the First Wizarding War and therefore would be a perfect example of the kind of person Barty Crouch Jr. hates the most.
For example, when Imperiused, Neville Longbottom was able to perform a series of "quite astonishing gymnastics" under the curse that he would not normally be capable of. It is possible for someone who has been Imperiused to place others under the curse as well.
Who was the last boy to go into the Department of Mysteries?
This boy (Later discovered to be: Barty Crouch Jr.)
was a summer intern at the Ministry of Magic sometime before early 1995 and worked at the Department of Mysteries. He went missing within the Department.
After he was brutally killed by Lord Voldemort, Moody's dead body tragically fell from his broom. Moody, who was also prepared for every type of dangerous situation, became the first victim in Deathly Hallows: Part 2. Mad-Eye Moody's death only occurred because of a betrayal, which makes it incredibly harrowing.
In Harry Potter and the Deathly Hallows Part 2, Neville is actually the person who destroys Voldemort's last Horcrux in Nagini, rendering him mortal, meaning that he and Harry truly delivered the final blows to Voldemort.
This was proven by the fact that in one of the alternate timelines, in which he was humiliated during the Triwizard Tournament, this feeling of embarrassment eventually led him to join the Death Eaters.
Voldemort Aside, Harry Potter's Highest Kill Count Belongs to a Surprising Hero. Harry Potter's Lord Voldemort undoubtedly has the highest body count in the series, but one unlikely wizard could offer strong competition.
Harry describes Umbridge to Sirius Black, saying that she's vile enough to be a Death Eater, despite not being one. Umbridge is also depicted to be a prejudiced person, despising half-breeds and Muggle-born witches and wizards to the point of firing Hagrid due to his half-giant birth status.
Although it is not confirmed to have been the Killing Curse, it is highly likely that Ron attempted to kill Voldemort's snake, and last Horcrux, Nagini, with Avada Kedavra. This is because, in the movies, Ron can be seen firing out a green spell at the snake, and it looks just like the Killing Curse.
After the Wizards' Council was reformed into the Ministry of Magic, tighter restrictions were placed on the use of certain kinds of magic. The Imperius Curse was deemed by the Ministry to be Dark magic, and, along with the Cruciatus and Killing Curses, were declared "unforgivable" in 1717.
Effect. Unforgivable Curses are the three most powerful and sinister spells known to the wizarding world, and are tools of the Dark Arts. They were first classified as "Unforgivable" in 1717. They are the Killing Curse, Avada Kedavra, the Cruciatus Curse, Crucio, and the Imperius Curse, Imperio.
Dolores, though, wrongly believes him to be attempting to speak to Dumbledore - who is wanted by the Ministry of Magic for treason. In order to coax information from Harry, Umbridge demonstrates a willingness to use the Cruciatus Curse to 'loosen his tongue'.
She was enraged when Harry spoke Voldemort's real name and mentioned his status as a half-blood. This enraged her so much that she actually tried to stun him before Lucius deflected her spell with a Shield Charm, not wanting to inadvertently harm the prophecy they were sent to retrieve.
Inevitably, however, Karkaroff was finally tracked down to a shack in the north of Britain. He was killed by his former Death Eater comrades, as the Dark Mark had been cast into the sky above it, and Karkaroff's body was found in the shack itself for his disobedience to the Dark Lord.
Viktor entered the maze behind Harry and Cedric, and began searching for the Triwizard Cup. During the task, Barty Crouch Jnr, posing as Alastor Moody by way of the Polyjuice Potion, managed to place the Imperius Curse on Viktor as part of his plot to steer Harry Potter to victory in the Tournament.
Having devoted his entire life to catching dark wizards — with high ambitions of becoming Minister for Magic one day — Crouch Sr. disowns his son in front of the entire Wizengamot despite his desperate pleas. He uses his son's trial as a public example of how Death Eaters should be punished: a life sentence in Azkaban.
