If a creature didn't die before your end step begins, the ability of Liliana's Scrounger doesn't trigger at all. The creature may have died before Liliana's Scrounger entered the battlefield, however.

If you control more than one Liliana planeswalker, you choose which one receives a loyalty counter as the ability of Liliana's Scrounger resolves.

The triggered ability triggers just once, no matter how many creatures died this turn.