Lions do not have many natural predators; humans, other lions and hyenas are sometimes known to kill lions. The lion is referred to as the king of the jungle, but hyenas will sometimes kill them when they are injured and the hyena is extremely hungry.
The largest predator of the lion is the human. Humans will kill these creatures out of fear for their lives, out of traditional burial practices and as an act of bravery in front of other people. They are not commonly killed to be eaten and are generally only killed for the sport of the hunt of lions. They hunting of lions is not necessarily bad and can help keep humans safe.
Lions sometimes have to fight other male lions for the females in the pride or for the food that has been brought back by the females. These fights are vicious and are among the most common reasons that lions are killed. When lions fight each other, one of the lions generally ends up dying as a result of the fight. This is not technically considered to be predator behavior, but often qualifies as it because the lions have very few predators in the natural world.