Index & Lookup returning data for only 1st or last occurance of matched key value.

Building a spreadsheet which matches values in a 2 column table and returns the
value for each occurance of the key value. So far able to get the first key value occurance using "=IF(INDEX($A$2:$B$8,MATCH($K28:$K34,$A$2:$A$8,0),2)=K$19,"X","")"
and the last key value occurance using "=IF(VLOOKUP($K10:$K16,$A:$B,2,1)=K$1,"X","")".
How do I get the formula to return info from all occurances of a repeated key value in the look up table?