Remove both duplicate and original value from Excel or Google sheet

=if(countif(A:A,A1)=1,0,1)

There is a zero or a one in Columns C for each value in Columns A. A zero means that a value from Columns A is not repeating in the data range and should be kept. A one means that there are duplicate values and that row should be deleted. Then filter the rows having One in column C, Select and Delete.