Answer:
I would have to say Walter ( or Mama )
Step-by-step explanation:
I say Walter because throughout the whole play we watch him struggle. We watch him struggle with his desire to have money and become rich. But at the end of the play we see that Walter realizes that sometimes dreams just don't come true (or they are really hard to achieve) and he finally did something that wasn't self centered around himself. He told Mr. Lindner that they wanted to move into the house and that they did not want to accept his offer. Mama can also be a hero because she is what hold the family together but I really believe it's supposed to be Walter.
Hope this helped!