Lee sins kit is so overloaded.
He is the perfect champion he has literally everything you need to carry. Two percent health abilities. Two gap closers. A slow. A knock up, knock back kick. Two true visions. A shield. An ability that gives spell vamp and life steal.
His only downfall is that he's "Difficult" to play. Although this is what I observe people who are Decent at lee do extremely well, and people who are amazing at Lee absolutely destroy. He builds bruiser and out damages tons of champs or he builds full AD and blows up everyone.