Tigers and Lions are both natural predators of the Leopard and if a leopard comes up against a Lion or Tiger the Tiger and Lion could attack and kill the Leopard.
The Leopard would usually try it's best though to get away from the Lion or Tiger before it has a chance to attack it but sometimes the Lions and Tigers are very fast as well and can get the leopard even as it's running away.
Leopards make great food for Lions and Tigers and the Leopard usually stands no chance at survival of the Lions or Tigers.
A bear such as a Grizzly bear can also kill and eat a Leopard if it wanted too.
Also humans are another animal that kills Leopards and eats them.
Yes us humans are an animal species.