Roommates, you either love them or hate them.
If you've had more than a few roommates in your lifetime, then it's likely you have a few that you absolutely detested. Some people just don't know how to live with others, and don't seem to have the self-awareness or care to learn.
But there's a big difference between someone who loads the dishwasher differently and someone who stiffs you on rent, eats all your food, and has loud sex in the living room.
In a popular Ask Reddit thread, people shared what made their "worst roommate" so bad.
1. From Electro-Onix:
Was a slob who got into drugs and hanging around the wrong sorts of people.
Completely trashed his room and took off one day leaving his dog he had just gotten behind for me to deal with, along with a bunch of unscrupulous looking characters knocking at my door telling me that he owed them money and asking where he was.