* Following Voldemort's orders: Crouch Jr. was a devoted follower of Lord Voldemort, who had ordered him to kill Harry. Voldemort believed that Harry was the only one who could defeat him, and therefore needed to be eliminated.
* Desire for power: Crouch Jr. craved power and saw Harry as a potential obstacle in his path to achieving it. He believed that by killing Harry, he would gain Voldemort's favor and rise in the ranks of the Death Eaters.
* Personal grudge: Crouch Jr. held a personal grudge against Harry. As a student at Hogwarts, he had been bullied by Harry's father, James Potter, and resented him for it. He saw Harry as a symbol of everything he hated about his father and his past.
* To fulfill Voldemort's prophecy: Voldemort believed that Harry was destined to be the "Boy Who Lived" and that his death would ensure Voldemort's own immortality. Crouch Jr., as a loyal follower, was determined to make this prophecy come true.
Ultimately, Crouch Jr.'s actions were driven by a combination of blind obedience, ambition, and personal vendetta. He was a dangerous and ruthless individual who was willing to do anything to achieve his goals.