Illumi Zoldyck is the eldest Zoldyck assassin in Hunter x Hunter, known for his blank expression, long hair and unnervingly gentle way of speaking. Short clips of his dialogue circulate on soundboards and in anime edits because a single word can change the mood of a scene. The wonderful line is shared as a standalone reaction, separate from its original episode context, and is reused in memes where calm approval sounds more dangerous than anger. Its popularity comes from that recognisable voice and character, not from volume or a jump scare.