Killua Zoldyck was the secondary protagonist of the Hunter X Hunter series and a young boy trained to become a deadly assassin. His character has progressed well alongside Gon as the anime has continued, advancing as peers and friends rather than rivals.
Despite the invaluable aid he has lent to Gon's journey in finding his father, Killua has as many flaws as would be expected of a dynamic and realistic character. By analyzing his greatest strengths and juxtaposing them with his worst weaknesses, we can better appreciate his merits as a fighter and comrade.
10 WEAKNESS: His Dark Past Has Been Exploited & Turned Against Him
Killua's time with the Zoldyck family did not come without cost. Illumi gained such a pernicious influence over him that he managed to brainwash him into killing Bodoro in the Hunter Exam and therefore forfeiting his chance to procure a license.
Though he was able to pass the second test he took (with considerably more ease) after learning Nen under Wing, his brother's influence demonstrated how his morbid past and conditioning haunt him long after leaving the homestead.
9 STRENGTH: Killua Has An Incredibly High Pain Tolerance
Although what his family did to him was atrocious, the torturing made Killua develop an absurdly high pain tolerance that would enhance his capacity as an assassin.
Regardless of how badly Milluki flogged him, he refused to recant the values he'd learned from Gon Freecss or agree to inherit the mantle of leadership his father wished for him. The fortitude he learned at home would be a massive asset during the Chimera Ant arc, where the heroes faced the threat of pain and worse in countless situations.
8 WEAKNESS: Killua's Durability Isn't Particularly Remarkable
Killua may have the benefit of pain tolerance, though that doesn't translate into a direct resistance against physical harm. He knew how easily he would be overwhelmed by Youpi in an even fight and was therefore obligated to work with Knuckle in order to topple him.
Unfortunately, he has never illustrated considerably high durability, especially when compared to his compatriot, Gon Freecss. However, Killua's ability to compensate with other skills allows him to remain viable in a fight even if he cannot withstand as many attacks as his friends or adversaries (except with concentrating his Gyo).
7 STRENGTH: Killua's Automated Reflexes Provide Alacrity In Battle
During his fight against Youpi, Killua awakened the next level of his Godspeed abilities, and he was able to move so fast that dodging was almost intuitive. This complemented his already stellar speed and allowed him to utilize it in battle to its fullest potential.
Perhaps more importantly, it allowed him to compensate for his previously mentioned low durability and continue the battle against a royal guard who could rip through rock and steel alike with ease. If not for his adaptability, he may have faced the same failure as his predecessor, Shoot McMahon.
6 WEAKNESS: Killua's Jealousy & Stress Are Sometimes Toxic
Killua has often displayed insecurity over his friendship with Gon and understandably so. Gon was the first true comrade he'd made and completely changed his outlook on life.
However, Killua's decision to stalk him while he was on a date with Palm was foolhardy. Although he had decent reasons for pursuing the couple (as the woman was clearly not in a sound state of mind), he would have compromised her scrying services if he'd been caught lurking in the shadows.
5 STRENGTH: Killua's Loyalty Is Unquestionable
Killua may sometimes come across as jealous, though his actions bely the deep fealty and allegiance he feels toward his friend, Gon. He refused to give him up to his family and agreed to help him find his father (and later, Kite) during their exploits in the NGL.
When Gon was critically injured in the aftermath of his victory over Neferpitou, Killua used his younger sibling's miracle-working to see his health restored. This was in spite of the fact that doing so attracted the ire of Illumi and Hisoka - both villains considerably stronger than he was.
4 WEAKNESS: Killua Is Naturally Pessimistic
Killua's pessimism is a stark contrast to Gon's optimism, allowing for the two to play off of each other well. During Isaac Netero's surprise test at the gym, he was the first to give up on seizing the ball from his hands or forcing him to break his own conditions of the game.
After he left, Gon continued to try his luck and was eventually successful in getting Netero to switch which of his hands held the ball. Although it wasn't sufficient enough to earn his license, it filled Gin with a warranted sense of accomplishment and proved that he was his father's son.
3 STRENGTH: Killua's Pragmatism Is Oftentimes Necessary
While Killua's pessimism may inhibit how he pursues his dreams, it can also serve as a necessary asset in the boys' mutual survival. After Kite sacrificed himself so that they could escape Neferpitou, he had the common sense to run before it was too late - and to coax Gon into doing the same.
Additionally, he is much more willing to kill potential threats than Gon was, minimizing the number of adversaries the heroes might come across in an already precarious landscape. This was especially true in the Chimera Ant arc.
2 WEAKNESS: Killua's Dependency On Gon Is Unhealthy
Killua's loyalty may be an admirable quality, but much of his identity has been constructed around his relationship with Gon. This creates a toxic dependency out of what would otherwise be an endearing friendship, especially when Gon's own objective (to find his father) had little to do with Killua's sense of self.
Fortunately, the assassin began to ossify his own identity after Gon's hospitalization at the end of the Chimera Ant arc, where he vowed to look after Alluki and protect them from threats once his friend had been properly restored.
1 STRENGTH: Killua's Teamwork Is Phenomenal
Killua's ability to synergize with his comrades renders him an invaluable asset in whatever challenge he works toward. Though he is (predictably) the most compatible with Gon, he has illustrated a competence in working with others on numerous occasions.
He collaborated alongside Knuckle in order to defeat Youpi and was even able to work with Hisoka against Game Master Razor during the events of the Greed Island arc. His teamwork skills allow him to harness his speed to its greatest potential.