- I’m a 26 year old guy who hasn’t watched X...
- I’m a 26 year old guy who haven’t watched X... Which one would be accurate?
Who has? I have.
Who has it? I have it.
Don’t be confused by the contractions “hasn’t” and “haven’t.”
Here, ￼who works just like she, he, or it. It’s a third person singular relative pronoun. There are no plural subjects in your sentence.
I have, you have.
She has, he has, it has, who has.
So to answer your question:
I am a guy who has a shirt.
I am a guy who has many shirts.
I am a guy who wears many hats.
I am not a guy who has been arrested.
I am a knight who has not been defeated.
Who can be plural.
Who is plural when it refers to more than one person. Then it takes “who have”, like “they have”.
The teachers who have quit are Alice, Bob and Carl.
The only teacher who has been fired is David.