On the surface, it’s easy to dismiss the Underground Man as petulant, rude, stubborn, and silly. However, he is actually a complex character and is, in some ways, admirable. In this discussion, I’d like to hear your thoughts on the ways in which the Underground Man is admirable, heroic even.

The Underground Man himself denies that he is a hero and, indeed, it is hard to see him as one.
One could say that the Underground Man is admirable in how he is willing to cast a critical look at society. Many people overlook the negative aspects of life, or how cruel society can be to the unfortunate and poor, while the Underground Man does not; he does take this way too far, so it might not be the best example. However, he is willing to see what is undesirable in himself. In this regard, he is no hypocrite. He admits he is conceited and spiteful, and does not pretend he is a great man, even if he wishes to be admired for his intelligence.
The Underground Man also never asks for the reader's pity. He might inspire it through his inner pain and loneliness, but he does not demand that we feel sympathy. This could be viewed as admirable.
Additionally, his choice to retreat from the world might be seen as admirable. He hates the games society plays, and instead of stomaching rules he cannot stand he opts out entirely, so as to avoid hypocrisy in this regard.