The 1st strongest Avenger is generally considered to be Thor.
Thor, the God of Thunder, has consistently been portrayed as one of the most powerful beings in the Marvel Cinematic Universe. His immense strength, durability, ability to summon lightning, and command over the storm, coupled with weapons like Mjolnir (and later Stormbreaker), make him a formidable force. While the power levels of other Avengers have fluctuated and some, like Captain Marvel and Scarlet Witch, have showcased immense power, Thor's consistent displays of raw strength and godly abilities place him at the top. He has consistently demonstrated the ability to take on exceptionally powerful foes, and has been cited as one of the most powerful Avengers by fans and in-universe characters alike.
While the power rankings of Avengers are often subjective and dependent on the context of the story, Thor's long-standing status as a god and his feats of strength firmly establish him as a prime contender for the strongest Avenger.
