I believe you are referring to EXO's Kai's nickname.
It is written as 깜종 in Korean. It is short for 까만 종인 (kkaman Jongin) which means "black Jongin".
Anyway, you should not have expected people here would know what it means because it is only known within the fandom. There are not a lot of Kpop fans here, let alone EXO fans.