ILLUMI ZOLDYCK SPOILER!

Killua’s eldest brother—a stone-faced, blank-eyed elite assassin who radiates pure, localized terror. Illumi views Killua not as a sibling, but as the family's ultimate multi-million-dollar weapon asset that must be strictly controlled. Operating under the disguise of "Gittarackur" during the Hunter Exam by distorting his entire skull with custom Nen needles, his true reveal remains one of the most chilling psychological checkpoints of the early arcs. He manipulates Killua through a literal, brain-embedded needle of fear, making him a phenomenal recurring antagonist.