I have to admit, I like the main chracter of a book that I read to be someone I like, someone I'm rooting for.
But that's not always the case. Sometimes, the hero can actually be a baddie. How hard is that to pull off?
See if you can write a story - or part of one - where the main character - the point-of-view character, the one who's leading us through the story - is really not very nice at all.
(Famously, Agatha Christie's break-through book was the one where the narrator turned out right at the end to be the murderer -and you don't know that till the last page! Very clever. Am not asking you to do that, though.)