During the task, Barty Crouch Jr, 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. Under Moody's control, he caught up with
Moody also reveals that it was he who told Cedric to open the egg underwater and that he gave Neville the book that led him straight to discovering gillyweed in it. Harry realizes that Moody put his name in the Goblet of Fire and that he bewitched Krum.
Barty Crouch Junior soon arrived thanks to using the Marauder's Map, and while Krum wasn't looking, he hit Krum using a Stunning Spell. Crouch Junior then killed Crouch Senior, and hid his body under his Invisibility Cloak. Harry got back with Dumbledore, who revived Krum and sent Rubeus Hagrid to fetch Igor Karkaroff.
He was not corrupted; he was Imperiused. Bartemius Crouch Jr, under the guise of Alastor Moody, performed the Imperius Curse on him. This was done to make Harry's path to the Triwizard Cup clear.
Though the tournament was meant to be friendly, it was revealed to be a part of a plot to resurrect Lord Voldemort. Sadly, this led to Viktor Krum, whose headmaster was a Death Eater, being hexed to aid in their attempts. In a way, this became a...
Being in second place, Krum enters the Third Task maze after Harry and Cedric. Harry finds him performing the Cruciatus Curse on Cedric, Stuns him, and signals that he is out of the competition. It turns out later that Krum was being controlled at the time by Barty Crouch Jr. using the Imperius curse.
Viktor Krum was third, facing a Chinese Fireball. He used the Conjunctivitis Curse to blind the dragon and retrieve his egg. However, he was docked points when the dragon stumbled around and smashed half of the real eggs.
Transfiguration and Animagi are different
For example: if Viktor Krum can transfigure his head into a shark's, like he does in Goblet of Fire, that doesn't mean he is an Animagus. Transfiguration is a form of spell-casting, whereas becoming an Animagus is forever. And yes, he could turn into a falcon. Lucky.
Fleur Delacour failed to finish the second task because she was attacked by the grindylows. Because Delacour failed to finish, she never retrieved her younger sister, Gabrielle.
Later life
After the match, a tearful Krum announced his retirement. However, Krum's ambition to help Bulgaria win the Quidditch World Cup made him come out of retirement to compete in the 2014 Quidditch World Cup.
Barty Crouch Jr.'s Malfoy Hate Explained
His hatred of these sorts of Death Eaters probably stems from being locked in Azkaban for years for his service to Voldemort while others, like Lucius, walked free.
Sirius scolds Harry, "what do you think you were playing at, walking off into the forest with Viktor Krum?" (29.92). And during the third task, Viktor casts the Cruciatus Curse on Cedric Diggory until Harry comes along and Stuns him. (It turns out later that Moody used the Imperius Curse on Viktor to make him do this.
In 1994, Moody accepted Dumbledore's offer to teach Defense Against the Dark Arts for a year, but was captured and imprisoned by Barty Crouch Jr., who impersonated him during the 1994–1995 school year, in order to send Harry Potter to Lord Voldemort.
Despite his skills, the Irish side were too good for the Bulgarians, and Viktor decided to end the match by catching the Golden Snitch. During his pursuit of the Snitch, he was hit in the face by a Bludger which broke his nose and gave him two black eyes.
Did Hermione sleep with Viktor Krum? No. Keep in mind that for her entire fourth year she was 15 - a year under the age of consent in the non-magical world. And even if the magical world had different rules, she would still have been raised by parents who taught her better.
Alastor “Mad-Eye” Moody is a Hufflepuff.
Weasley hates Fleur because she's "too pretty, too flighty, not as smart as Tonks". Fleur's arc is proving that she is as smart and strong as any other female character. It's not her fault she's so pretty when she couldn't control how she looked. She's not flighty or as rude as Hermione, Ginny and Molly think she is.
I think it's because Fleur was always quite arrogant, and I think Molly didn't want her to be with Bill. She thought they were only together for the physical side if things. Ginny didn't like her because Fleur treated her like a little girl, not like a respected teenager like Ginny was used to.
Relationships with Other Characters
Ron Weasley accidentally asks Fleur to attend the Yule Ball with him; she ignores him. Harry suggests that this because she has turned on the charm to try to ensnare Roger Davies, and Ron had been caught in the flux of her spell.
Animagus. Lily's animagus form is a Doe, coupling with her husband, James Potter who is a Stag. Severus Snape's animagus is also a Doe.
Was Voldemort an Animagus? No, Voldemort was not an Animagus. He didn't see any reason to become an Animagus despite being a gifted wizard and knowing a lot of magic. This may simply be because his sole purpose was to obtain immortality and become the strongest wizard who could control the world around him.
Cedric's death is a major plot point in the stage play Harry Potter and the Cursed Child, in which Harry and Ginny Weasley's son Albus uses a Time-Turner and prevents Cedric's death. Due to his humiliation in the Triwizard Tournament, Cedric eventually becomes a Death Eater and kills Neville Longbottom.
All of the champions got the egg eventually, but Cedric and Fleur were charred a bit, and Krum causes his dragon to step on several of her real eggs. Ron and Harry are reunited afterwards, as Ron was terrified for Harry's life and realized that Harry would never put himself in that position just for attention.
They succeeded, but unfortunately did so in such a way that Cedric Diggory ended up looking the fool in front of everyone assembled to watch for the second task. Seething with fury at his humiliation, Cedric ended up joining the Death Eaters come Voldemort's return.