What makes Blanche Dubois and Stanley Kowalski different from each other in A Streetcar Named Desire?

The main characteristic that differentiates the character
of Blanche Dubois from the character of Stanley Kowalski in the play A
Streetcar Named Desire is their upbringing. Their diverse and complex origins
played an important role in how they developed as adults. Ultimately, it would make
their differences so remarkable that they ended up hating each other until the final
tragedy occurred.

Blanche and Stella Dubois grew up as
Southern "aristocrats". Their family had a solid financial foundation and none of the
two girls had to work for much. They were maybe even spoiled, and always waiting to get
what they wanted. Before the fortunes of the Dubois family came spiraling down, it was
Blanche who had to face the situation. As a woman with little knowledge of poverty and
struggle, Blanche had to come up with ways to survive in a society that she did not
understand. She lost everything: Her dignity, her self-control, her reputation, and even
her place in society, due to the myriad of bad choices she made with sex and alcohol.
Ultimately, she chose to become the embodiment of the very dignity that she lost after
she became a nobody. Hence, she would walk around pretending to be a snob,
over-dressing, hiding the horrid things about her past, and still maintaining that she
had rich friends to help her out.

These very qualities were
what made Stanley Kowalski detest Blanche so much. Stanley was a blue collar, former
military man with a no-nonsense attitude towards life. He was rough, dingy,
chauvinistic, and misogynistic. Also, he was a loud and obnoxious drinker and gambler.
He had no concern for the needs of his wife or any other woman, and he treated women
however he pleased. He beat up his wife whenever she made him angry, even when she was
pregnant. He demanded to be respected as the "man of the house", and the presence of
Blanche threatened him. In the end, he discovered that the very judgmental and snobby
Blanche had nothing to be so proud of. He then showed Blanche how he could have control
over her by exposing everything that he found out about her. At the very end of the
story he rapes Blanche, leaving her so traumatized that she ends up in a sanatorium.
Stella did not care.

Hence, the origins of Blanche and
Stanley were so diverse and so complex in their own right that none of them could have
ever crossed paths in life without a catastrophe.