How to loop through a column and return non duplicates?

Looping through one column for a condition and returning non duplicate values of another column

I’m trying to go through column A for a certain condition, and if that condition is satisfied return column B but only the non duplicates of that.
In the very simplified example below

2 test
2 test
2 test
3 mailbox
5 deleted

If column A condition is “2” I just want to return a new column with one cell populated as “text”

Can anyone here give me the right direction as to how to loop a column for a certain condition and return another’s value?