The more recent question:

Is this correct? "One of the things that makes him great is..."

One of the things that makes him great is he brings it every night.

I'm pretty sure it should be "that make him", because one of the things is referring to a lot of things ...but I always see native American speakers say it with an s.

Another example:

This is one of the responsibilities that comes with greatness and he understands that.

They always use the word with s even though it's grammatically incorrect.

The question it is supposed to be a duplicate of:

"One of them was/were you"

If I am talking to somebody about a certain group of people in the third person, and then want to refer to the person I am talking with as one of those people, which do I say?

One of them were you

One of them was you.

Surely this is a mistake and the more recent question should be reopened?