Bad / Strange
pest - An annoying or troublesome person, animal, or thing; a nuisance
The flies in my room were such pests that I couldn't get rid of, that they prevented me from concentrating on studying for my final exams.
boor - A rude or insensitive person, who doesn't have good manners.
Their son Roger was a loudmouthed boor who emabarrased his family at every social event they attended.
inconceivable - Not capable of being imagined or grasped mentally; unbelievable
When Roger Banister ran the first mile in under 4 minutes, he achieved what people had thought was an inconceivable accomplishment.
alien - Someone who is strange, different, foreign, and not from 'here'.
When the foreigners tried to integrate with the new country, they were excluded from everything and were just treated like aliens.
unreliable - Undependable, untrustworthy; an unreliable
When Alan showed up an hour late for their date, Maxine lost interest in him, because she concluded that he was just an unreliable person.
pariah - An outcast, someone who is disliked and rejected.
Even though North Korea is regarded by most countries as a pariah government, people don't mess with them because they have an atom bomb.