Lions are at the top of their food chain, meaning nothing eats it, but this is not strickly true, it is only true for fully grown lions, not cubs.
But sometimes lion cubs can be eaten by jackals, hyenas, leopards, martial eagles and snakes. Also buffaloes, should they catch the scent of lion cubs, often stampede towards the thicket or den where they are being kept, doing their best to trample the cubs to death whilst warding off the lioness.
Furthermore, when one or more new males oust the previous male(s) associated with a pride, the conqueror(s) often kill any existing young cubs, perhaps because females do not become fertile and receptive until their cubs mature or die.
no- one