"There wasn't a single person, except for one person."
Okay, first it was clearly two people.
Second, if you removed the second use of the word "person" from the very end, then it would actually be correct English, despite what the people complaining say. Yes, that is how English works, because English rules are weird and non-nonsensical. That's what happens when different languages with different sentence structures get forcibly mashed together into a single language.