I looked at your very small example and do have a few more questions.
First let me explain how this might be accomplished.
First of all there is no such formula that will do this it will need some VBA.
The first part is relatively easy, look for duplicates in column D,B. and delete any row that has no value in column P. This will leave the row containing column P automatically.
Now is where it gets tricky.
If you want to retain data from other rows, it will significantly increase processing time/cost as now blanks anywhere have to be replaced with any potentital data. And the way excel accesses the computers CPU is not the most efficient for this kind of work.
Now the problem occurs when what happens if say for example you have 3 duplicate rows and they have 3 different values in column P or any other coluimn. How does the program prioritize which one to keep and which to delete.
One such way might be to delete 2 of the rows, but copy any extranious data into new columns. Perhaps you can say what the most important data is and those could be copied into new column to the right of the row we are keeping. But this might not look very good, but atleast the data is retained.
Other option is to copy the entire row that is being deleted to another sheet. so you have a master list of the retained data but still have a backup of the original deleted data somewhere that you can refer to.
So ultimately I would suggest we do this is multiple steps. first do the minimum, just delete any duplicates that have empty column P. THen once that is in place, we can open new questions and see if there is more that can be done with the program.
here are my questions.
1. What version of excel do you have.
2. Is this list contained in multiple workbooks or multiple sheets within a workbook.
3. Is each list unique, meaning that list 2 wont contain any duplicates of list 1, meaning that there will not be a duplicate row in the 2nd list that is a duplicate of any row in the first list.