What about Natasha Romanoff, otherwise known as Black Widow? She doesn’t have a space hammer or a giant green form, but her elite training and gadgets allow her to handle any human opponent, and she can infiltrate any facility or assassinate any target. But she’ll need a partner. Who in the MCU would be a good partner for Black Widow, and who would be a poor fit?
Gamora is a humanoid alien who was adopted by Thanos in her girlhood, and she has undergone some serious training. She is a master of the sword, and martial arts come just as easily to her. Up close, not many opponents can stand up close to her for long.
What is more, Gamora is serious, practical, and mission-oriented, and that puts her in the same league as Black Widow. In a way, Gamora is the Black Widow of the Guardians of the Galaxy, so she’d be a natural fit for the human Black Widow
This caped gentleman is the master of the mystic arts, and he even had the Time Stone on his person. Dr. Stephen Strange was a surgeon who learned to master magic, and he has been slinging sorcery and speaking metaphysically ever since.
Dr. Strange is a powerful ally on a chaotic battlefield, but his mind-bending sorcery would disorient Black Widow. Furthermore, Doctor Strange has no interest in Black Widow’s kind of mission anyway. He’d make for a pretty awkward partner, to say the least.
Just because a character has a lot of strength and abilities, doesn’t mean they are the ideal choice for a given mission. Some assignments call for proper warriors, while other jobs require hackers, sleuths, infiltrators, or assassins. Thor is strong, but he can’t do everything. And sometimes he acts rashly or gets the wrong idea.