[Mild Spoilers Below:]

Kalluto has a silent and obedient personality, often seen doing what he is told. He is established to have a very good relationship with his mother. While he is very quiet, he has shown to be more talkative after joining the Spiders. He is also shown to be quite calm with good control of his feelings. Nonetheless, he proves during his fight against a Chimera Ant that, despite his calm demeanor, Kalluto has a brutal side and a bad habit of dragging out a fight in order to toy with his victims. Though Kalluto seems to be confident, he also displays a habit of questioning his skills and abilities when he feels that he is not good enough. Despite this, Kalluto possesses an inner resilience and determination, as seen when he reaffirms to himself that he is accustomed to enduring pain and hardship, then swears to get his brother back even when realizing his massive inferiority to other Phantom Troupe members,

Videos you may use as reference:
Kalluto vs Ant: https://www.youtube.com/watch?v=NdSry0XmZ2Q&ab_channel=ThePsychicPillar

Kalluto is out of their league [Eng]: https://www.youtube.com/watch?v=HJGL4F2pvfg&ab_channel=Totero