LEON:https://en.wikipedia.org/wiki/Giants_(Greek_mythology). Possibly a Giant, he is mentioned by Photius (as ascribed to Ptolemy Hephaestion) as a giant who was challenged to single combat by Heracles and killed.Photius, Bibliotheca Codex 190. Lion-headed Giants are shown on the Gigantomachy frieze of the second century BC Pergamon Altar.Pollitt 1986, p. 105; Pergamon Altar image viewer.
Leon:http://greekmythology.wikia.com/wiki/Leon (Λεων) – Leon was a leonine Gigante slain by Herakles in the war against the gods. The hero made a cloak of his skin. A lion-headed Gigante does occur in the famous Pergamon reliefs depicting the War of the Giants. The God that helped him is unknown.
Leonhttp://greekmythology.wikia.com/wiki/Leon (Gr: Λεων) was one of the Gigantes who tried to take Mount Olympus. While it was true that to kill a Gigante a god or goddess needed the help of a mortal hero, the opposite is not necessarily true. Leon is an example of that.
Ancient Text: “Herakles did not wear the skin of the Nemean Lion, but that of a certain Leon (Lion), one of the Gigantes (Giants) killed by Herakles whom he had challenged to single combat.”
– Ptolemy Hephaestion, New History Book 5 (trans. Pearse) (Greek mythographer C1st to C2nd A.D.)