Suppose you want to eliminate entries [usually for a Column] found more than 1 time, all you need to do is use the Filter. No, not the normal Filter but the Advanced Filter.

Choose the column where you want to eliminate duplicate entries, goto Data>Filter>Advanced Filter>Unique records only. This will eliminate all your duplicate entries but keeping only one common entry.

Also if this wants to be done for 2 columns respectively, then the Column with a higher number of Unique records will be considered first before filtering the Column with fewer Unique records.