|“||Assassination — It's the family trade. We all take it up. My folks see me as an exceptional prospect. But I don't see that I should have to live up to their expectations.||”|
Conflicting with Killua's predisposition to kill is his unyielding loyalty to his friends and natural kindness. Often, Killua suffers immensely in attempts to help his friends without a single complaint. Killua puts others before himself without being concerned about his own health or even his life. Previously, Killua's greatest flaw was his fear of those seemingly more powerful than him (one of whom being his elder brother, Illumi). Killua had been trained as an assassin by his brother to be extremely cautious that he only engages in combat provided that victory is absolutely certain. This impeded him as a Hunter, as Biscuit stated more than once that victory is never certain, and that depending on the circumstances, a person has the potential to defeat a stronger opponent.
Killua was born as the middle child to a family of assassins, the Zoldyck family, showing great promise from birth. Killua has already mastered many killing techniques at a tender age and is set to be one of the best assassins the family has ever produced. At the age of three, he started on training by tailing other people. He was forced to join in battle in the Tower of Heavens martial arts tournament at the age of 6.