Just going by this sentence alone:
Thor pushed the old woman and he pulled her, he tried to move her, to trip her, to force her down, but she might as well have been made of rock for all the good it did.
"for all the good it did" Here, the "it" refers to all the actions that Thor had previously done to/on her.
For all the merit/good each of those actions Thor had done, she might as well have been made of rock.
Although those actions were done in good faith, hoping something good could come out of it... (it was unfruitful, useless, futile)
Stuart, the first answer was correct!