What is a synonym for unprecedented?

Both are correct.

Synonym means: a word having the same or nearly the same meaning as another in the language. Definition means: the act of defining or making definite, distinct, or clear / the formal statement of the...

The word no can be replaced in some contexts by none, negative, zero, or nothing.

He is a pronoun. The only synonym it has is to use the name of the person it refers to, i.e., "He is short." "John is short."

It's possible to use the person's name or one, he/she, the reader, thou, thee, y'all, or ye.