Who was the character that had a red dot on his forehead in The Avengers?

The character with a red dot on his forehead in "The Avengers" is Loki, portrayed by Tom Hiddleston. The red dot is a symbolic representation of his status as a trickster and his connection to the mystical powers of Asgard. Loki is the main antagonist in the film, using his cunning and manipulation to challenge the Avengers.