Earlier this year, Tom Hiddleston's Loki died a heartbreaking hero's death at the hands of Thanos in Avengers: Infinity War. It was quite the end for a character who was once such a massive villain that he invaded Earth. But just as his actions towards the end of his life caused us to rethink the God of Mischief, so too does an update to his official bio, which now reveals that Loki was under the influence of the Mind Stone in The Avengers.
A Reddit user noticed that Loki's official bio on Marvel.com was quietly updated at some point and now confirms a theory that has been floating around for some time. According to Loki's updated bio, Thanos offered Loki dominion over Earth, which would allow him to get back at Thor, in exchange for Loki getting Thanos the Tesseract, which we now know to be the Space Stone.
Thanos gave Loki the Scepter, which contained the Mind Stone. Loki used the Scepter to mind control others, like Hawkeye, but what Loki didn't know is that the Scepter was also "influencing him, fueling his hatred over his brother Thor and the inhabitants of Earth." This paints Loki's actions in The Avengers in a whole new light.
This revelation shows that Loki wasn't entirely responsible for his actions in that film, and he was being influenced and corrupted by the Mind Stone. In the comics, the Stones (Gems) have a mind of their own and it sounds like something of that nature was taking place here. The Mind Stone seemingly enhanced Loki's darkest feelings and ambitions making him more evil than he actually is.
Thanos almost certainly knew the effect the Mind Stone would have, and he conveniently failed to mention it to Loki. He instead allowed Loki to do his bidding on Earth, while the Mind Stone kept him doing exactly what Thanos wanted. It's not dissimilar to the one ring whispering to Frodo and influencing him the longer he held it.
In the first Thor, Loki is going through a personal and family trauma, coming to grips with who he is. After Thor defeated him, he was obviously hurt and angry and Thanos took advantage of that desire for revenge. The Mind Stone played on Loki's anger and enhanced it so that he went overboard in his retaliation by attacking Earth.
Loki doesn't even look like himself in The Avengers compared to the other times we've seen him. He looks strung out and sickly and we now know that is because he was under the influence of the Mind Stone.
Some might see this as a retcon, but it actually tracks with what we've seen so far. Although he was always an entertaining antagonist, the Loki we saw in The Avengers was simply put, much more villainous in that film than in his other outings. He was far crueler and his goals of domination left little gray area to him; he was an unambiguous bad guy.
Contrast that with everything else we've seen of Loki in the MCU. His goals throughout the Thor films have always been more mischievous, like impersonating his father and messing with his brother on Sakaar. He's a Trickster God and he likes to have fun doing bad things, but he isn't malicious.