One key element is his abnormal love for combat. He has always been drawn to fighting, even from a young age. Another is his lack of normal moral compass. This is evident as he does things just for his own pleasure in fighting.
Hisoka is a very interesting character. His origin story shows that he has always been a bit of an enigma. He was born with a rather twisted sense of pleasure, often finding joy in battles and testing his strength against strong opponents. From a young age, he was different from the norm, having a fixation on fighting and the thrill it brought him.
Hisoka's origin story involves his early days as a powerful and somewhat unhinged nen user. Key events include his discovery of his nen abilities and his growing fascination with strong opponents. He has always been on a quest to find and battle those who can give him a good fight, which led him to various parts of the world in search of worthy adversaries.
Hisoka is still alive in the manga. The storylines haven't led to his death yet. Maybe there'll be developments in the future, but for now, he's kicking.
Hisoka developed his unique fighting style through his constant battles and his natural inclination towards using nen in creative ways. He combined his physical strength with his nen abilities to create attacks that are both flashy and deadly.