Warning: Major spoilers for Avengers: Infinity War ahead.
While many fans would blame Star-Lord for Thanos' triumph at the end of Avengers: Infinity War, Thor is probably the one who fans should point their fingers at, according to the Russo brothers.
At the final showdown against Thanos in Wakanda, Thor had a chance to kill the Mad Titan with his incredibly powerful Stormbreaker. Thor's new weapon hit Thanos' chest, a move that allowed the Mad Titan to use his Infinity Gauntlet to wipe half of the universe. As Thanos told Thor, he should have aimed for his head, and the God of Thunder will definitely regret it since his aim was intentional.
Speaking to Comicbook.com, Joe Russo explained why Thor didn't aim for Thanos' head. "I would argue that the fan base could be equally upset with Thor, who chose to throw that ax into Thanos' chest and not his head," Joe Russo said. "Because he wanted to tell Thanos that he got revenge."
Thor is known for acting on impulse and emotion rather than seeing the possible long-term consequences of his actions. He was more focused on claiming his revenge than actually killing the Mad Titan for good.
"Had he gone for a kill shot, if that happened, these are choices that characters who are feeling immense pain make and hopefully, the audience can learn to empathize with those characters because they can grow through stories," Joe Russo continued. "Stories can teach us things and that we should try to see every choice from the perspective of the character that made the choice."
Since Thor is one of the heroes who survived Thanos' devastating snap in Infinity War, the God of Thunder still has a chance to redeem himself in Avengers 4, which is set to release in theaters on May 3, 2019.