No, look. I know I'm a disappointment, but you're wrong about humanity. They are your greatest creation because they're better than you are. Yeah, sure, they're weak and they cheat and steal and... destroy and disappoint. But they also give and create and they sing and dance and love. And above all, they never give up! But, you do!
Humans are the dominant species of Earth, gifted the soul by God some point after coming into being. Humans are considered God's greatest creation, however their favor would draw the ire of Lucifer, who saw them as flawed and murderous things. The view of humanity among the rest of the Host of Heaven varied, some like Castiel saw humans as works of art, while others like Uriel saw them as lower beings, referring to them as "mud monkies" and "savages" and comparing them plumbing on two legs, beliefs Castiel warned were close to blasphemy.
Nature? Divine. Human nature – toxic.
Throughout the years, Sam and Dean have encountered threats they believed to be supernatural, only to find that they were dealing with a completely human culprit, a fact which Dean frequently would comment on, revealing his disgust at the lengths people will go for to hurt others, calling them "sick" and "crazy", seemingly preferring to sticking to actual monsters.
The Winchesters first encounter with a human threat were the Bender family, consisting of patriarch Pa Bender, brothers Jared and Lee Bender and the youngest -- Missy Bender in Hibbing, Minnesota. The Benders would kidnap a man by the name of Alvin Jenkins while taking out the trash on night, leading to Sam and Dean arriving in town to investigate the disappearance, due to John marking the area as a possible hunting ground for a phantom attacker based on local folklore.
You know what humanity's greatest creation has been? Music. That and nacho cheese. Even I couldn't have dreamt up that deliciousness. But music... is magic. A lot of remarkable music was created in this space. B.G.'s Canteen. Now, it's not as well known as The Bitter End or The Gaslight, but some amazing musicians got their start on this stage. I'm hoping that you and I can tap into some of that old magic and finish what I started a few months ago.