The Avengers, Vol. 1 #138 (1975)

Stranger in a Strange Man!
The Wasp is gravely injured by the Stranger's attack, and is rushed to the hospital. Yellowjacket seeks revenge for his fallen wife. In a strange turn of events, the Beast discovers that the "Stranger" is actually Toad, an evil mutant who works under Magneto. Vision and Scarlet Witch continue their honeymoon.
Release Date: 1975