the bad guy (=a man in a book or movie who does bad things)
The bad guys all have guns.
the good guy (=a man in a book or movie who does good things and beats the bad characters)
He’s one of the good guys in the 'Star Wars' films.
a bad guy (=a person who is responsible for something bad that happens, or a person who you do not like)
I'm fed up with people always thinking that I am the bad guy.
Mike's not a bad guy.
the poor guy (=used when something bad happens to someone and you want to show sympathy)
The poor guy was robbed of all his money.
a tough guy (=a man who is strong and not afraid, especially one who is good at fighting)
He’s trying to prove he’s a tough guy.
a regular guyAmerican EnglishAmE (=an ordinary man)
I knew him in high school. He’s just a regular guy.
the little guyAmerican EnglishAmE (=ordinary people rather than a powerful organization such as a government or a large company)
He wanted to get elected and fight for the little guy.
Examples from the Corpus
guy• I saw a guy with a head the size of a bucket-the kind you put mops in.• I've put the finger on seven members of the ring since lunch, but the big guy is slippery.• Two chauffeurslinger in the corner, one white with blondhair, the other a good-looking black guy.• But you only need a few guys like me and you could.• It was sheerbloodyhelllistening to all those fatuousnincompoops saying what a great guy you are.• Dave's a really niceguy.• Nine guys played, and nine guys accomplished something.• Marriedveterans or guys who married when they got back had difficulties, too.• There's some guy who wants to talk to you.• Is he the guy who used to live next door to you?• These guys believed in what they were doing.
Originguy
1. (1800-1900)Guy Fawkes (1570-1606), who tried to blow up the English parliament.
2. (1300-1400) Probably from Dutchgei“type of rope”