Tonton Streaming ThunderCats (1985) S1E37 - Lion-O's Anointment First Day: Trial of Strength

On Lion-O's 20th birthday, he must pass a set of trials to become the true Lord of the ThunderCats. Even though he is the hereditary Lord of the ThunderCats, he must prove himself to be worthy of that title. His first test is to beat Panthro in a duel to test his strength.