{=INDEX(list,MATCH(0,COUNTIF($D$4:D4,list),0))}
// Replace A1:C4 with target Cell Reference/Range
=UNIQUE(A1:C4)
// for cells from X2 to X274 -> results will start from X276
// change the letter to match which column is used
=IFERROR(INDEX($I$2:$I$274, MATCH(0,COUNTIF($I$276:I276, $I$2:$I$274), 0)),"")
// then drag(copy) cell to below cells untill empy cells starts to show