Why so much damage?

I understand that some champs so so much damage but really. Jhin does so much damage early game to my support, its unreal. Not just that some champs like Xayah and vayne do so much damage too. And Why the heck does Jhin tank so much of my damage, i played as xayah and my attacks that usually 1 shot him does no damage to him. And Yes he has no tanky items!