Hunter x Hunter's Killua is one of the most popular characters in shonen anime, thanks to his nonchalant and brazen attitude while being badass in battle as one of the strongest transmuters. Killua starts out as a cold and callous individual, but as the show goes on, he becomes friendly with several characters, a far cry from where the character began. Much of Killua's stunted character development comes from his early childhood upbringing in the Zoldyck family, where the concept of friends seemed non-existent.