A foil to Stanley Kowolski, Mitch is always dressed neatly, he is respectful and kind, he speaks in a more refined manner--not coarse like Pablo. While Stanley takes off his shirt and goes around in his undershirt, Mitch will not remove his coat for fear he is sweating too much; he even says that the men should not be playing cards around the women.
However, Mitch has some of the male predator in him, just like Stanley. For, when he learns of Blanche's less than stellar reputation, he tries to force himself upon her. This assault leaves Blanche so forlorn that she becomes very vulnerable, leaving her as prey for the animalistic Stanley.
Mitch is passive, awkward, and easily manipulated. This is not direct characterization, but what we can infer as readers. He is be passive, as opposed to the larger-than-life Stan, which is the reason why Mitch continuously gravitates around him. While Stan vies for attention, Mitch duly cedes his way, allowing Stan to take over everything from card games to conversations, and to even telling Mitch to stay away from Blanche.
From that latter fact we can also describe Mitch as an easily manipulated guy. Not only did Stanley, toward the end of the play, manipulate him so that he moves away from Blanche. Blanche herself, whom we can easily assume had no true feelings for him but rather the need to be with someone, also manipulated him. We know as much in chapter 6 when Mitch coyly admits:
You need somebody. And I need somebody, too. Could it be — you and me, Blanche?
Mitch is also awkward in the way that he cannot seem to find the gumption to be his own person. He is a follower. He is still attached to his mother, and he is crassly inexperienced with women.
Stanley is the proverbial Alpha who leads the pack and diminishes everyone else with his large and brash personality. He is egocentric, as he demands all the attention from Stella.
He is also misogynistic, as he beats his wife, psychologically abuses Blanche and then rapes her. Stanley is nothing short of a sociopath that has not yet killed. It is clear that his ego is easily bruised each time Blanche attempts to use her Southern charm to annoy him playfully.
His insecurities lead him to take the upper hand and “get dirt” on Blanche so that he can have ammunition to destroy her ego and separate her from Stella. Stanley is essentially a broken man acting the part of a dominant macho man. Unfortunately for Blanche, Stella ends up siding with her husband and Blanch ends up in a mental institution and with no future.