He cuts himself off from society, hates everyone and anyone (one wonders why I love it so much). It was a great influence on the movie Taxi Driver (my favourite movie of all time). There are a whole lot of similarities between The Underground Man and Travis Bickle. Loneliness and paranoia are the themes most prominent in both book and movie.
Loneliness
Paranoia (NSFNACW (Not Safe For Non Art College Work))
here is....