The Final Chitauri
In 2012’s The Avengers film, the Chiatauri race was not something to be messed with. However, they did end up losing, as is typical with all villains. According to the film, no Chitauri remained. They weren’t ambiguous about this, either. They said that not a single Chitauri soldier was left intact. Someone lied to us.
In GOTG during the scene where we see The Collector’s impressive collection, you might’ve spotted a lone Chitauri on display in the background. Not only was it there, thereby proving that MCU scriptwriters’ pants are on fire, but it appears to be very much alive. Enslavement or collection? You decide.