To acquire the pack a punch in Blood of the Dead, you must have the shield. Once you have the shield you need to suck the life out of Zombies with your key in order to grab charges. Once you have once charge, you can go up to the roof to the power panel and blast it this will cause an electric surge to power though and two souls will make pack a punch.
However the pack a punch moves and can be in three locations, the roof, by second gen power room and finally first gen power room. Remember its random when and where it moves.
Quick tip, make sure to pack your weapon 4 times in order to get a much more powerful weapon,
