한 그

the … that [someone] did

→ 하다
phrase Rare #25,107
the … that [someone] did 한 is a past-tense modifier of 하다 (to do), and 그 means “that” before a noun. The exact meaning depends on the verb phrase and noun around it.
KO: 네가 만나기로 한 그 사람은 누구야?
EN: Who is the person you agreed to meet?

네 말은 차투르 랑 만나기로 한 그 왕두란 말 이지?

You mean the prince who was supposed to meet with Chatur?

— 세 얼간이 (2009)