12 Times Sam And Dean Were Basically Villains On 'Supernatural'

Sam's friend Amy was a Kitsune, a creature that feeds on people's brains. She saves Sam's life by slaying her own mother. As adults, Sam tracks Amy down after she's been feeding on people. He lets her go due to Amy once saving his life, as she promises to stop and because she only did it to save her son's life when he was very ill and needed to be fed.

Unfortunately, Dean tracks Amy down and ganks her anyway while her son watches. He doesn't care to see what will become of the orphan, and even threatens the boy that he'll be next if he becomes like his mother. Then, he just leaves the boy alone and motherless.

Jack decides to sacrifice himself to stop Chuck and Amara in order to get Dean's forgiveness for causing Mary's demise. All Dean has to do is accept Jack's apology, but he goes through with turning Jack into a bomb even when Castiel tries to stop him since Jack is his adoptive son.

Dean still doesn't care and has his own selfish motives to end Chuck and be free in his life. This, despite the fact that Jack is only three years old and doesn't deserve to perish in such a way. Dean even pulls a gun on Sam and is close to shooting him until he finds out that the plan of Jack's explosion has been a lie told by Billie the Reaper. 

Donatello and Kevin are both prophets and become involved with Sam and Dean because they can help the brothers in their mission. Unfortunately, once they fulfill their importance, the brothers make no effort when the prophets are in peril.

The Winchesters forget about Kevin when he's a lost soul on Earth and don't even try to help him. Meanwhile, they have no sympathy for Donatello after he loses his soul to Amara and even consider ending him if he starts exhibiting any negative attributes.

Jack loses his soul to end Alternate Michael's life and save the Winchesters. Rather than accept that the malevolence he exhibits afterward is because he doesn't have a soul and can't understand emotions anymore, Dean swears vengeance when Jack accidentally takes Mary's life after she pushes him too far. He then convinces Sam to trap Jack forever in the Ma'lak box, lying to Jack that they will cure him.

Jack became soulless for Sam and Dean, but the two have no care for his sacrifice and attempt to seal him till the end of time when they could have tried to get his soul back instead.

Adam is possessed by the archangel Michael and is pulled into Hell when Sam throws himself into Lucifer's cage to seal the devil with himself. While Dean convinces Death to save Sam, he doesn't try to rescue his other brother.

In Season 15, it's shown that Sam and Dean can enter the cage at any time by requesting that the Ruler of Hell open the passage, which means they let Adam remain in Hell for more than 10 years on purpose. The brothers always argue that family comes first, but this is their own brother that they abandon in Hell when they could've easily rescued him at any time.

Amara changes her ways after she realizes that humans and creation are beautiful things that need to be preserved. However, Dean devises a plan to capture Amara and end her existence because she balances the power of the universe, and since they intend to take out Chuck, Amara also has to perish.

Amara is essentially innocent and hasn't done anything to deserve this fate, but Dean convinces Sam to go along with finishing Amara's existence. He makes it worse by outright lying to Amara that he won't hurt her when he really hopes to wipe her out once she's captured.