Dude, this sounds AWESOME.
Like, I LOVE reading about morally gross people.
If you need things to write about, think about what made them that way. How would they react to situations? What is a situation for them that would be the worst thing to ever happen? Then BAM, write it.
Here are a list of movies with main characters that fit your description:
The Wolf of Wall Street – Young Adult – Quills – Inside Llewyn Davis – Filth – Bad Santa – Casino – Fight Club – The Master – American History X – Gone Girl – Reservoir Dogs – American Psycho – Magnolia – Fargo – Sin City – Psycho – Goodfellas – The Social Network – There Will Be Blood – Taxi Driver – Nightcrawler – Pulp Fiction – Monster – Bronson – The Killer Inside Me – A Clockwork Orange – Bad Lieutenant – Flight – Greenberg – Silence of the Lambs – Citizen Kane – Spring Breakers – Strangers on a Train – Closer – The Talented Mr. Ripley – Barry Lyndon – Dead Ringers – Dangerous Liaisons – Blue Jasmine
And that’s not including horror, cult, Shakepseare adaptations, or TV shows. Illustrious people have made big careers off of writing, directing, and acting characters who are not the best of us.