The Squadron Sinister is a supervillain team appearing in American comic books published by Marvel Comics. The Squadron Sinister first appeared in the final panel of The Avengers #69, created by Roy Thomas and Sal Buscema. The team is a pastiche of DC's Justice League.
The Squadron Sinister (left) battle the Avengers on the cover to The Avengers #70 (Nov. 1969). Art by Sal Buscema.
The Elders of the Universe are a group of supervillains appearing in American comic books published by Marvel Comics. The Collector was the first Elder to appear, and featured in The Avengers #28, but the idea that he was a member of a group known as the Elders was not introduced until The Avengers #174.
The Elders of the Universe surround Silver Surfer and Mantis on the cover of Silver Surfer vol. 3 #4 (Oct. 1987). Art by Marshall Rogers.