According to what you wrote above, one would have to be perfect.
There are different possible definitions. In the current context, I don’t think it was referring to perfection. I also don’t think it was referring to one of the lamed-vav-nikim or the Gedolei Hador.
I understood that it was being used in the colloquial sense of describing someone who is a “very good person” who has performed very big Mitzvos for which he will receive tremendous reward in Olam Haba.
I understood ZD’s question as being: “Can the term “tzaddik” be used to describe someone non-Frum the same way it is used to describe someone Frum?”
When someone Frum performs a lot of Chesed (for example), people refer to him as a Tzaddik even if he has many faults (as long as he’s not a serial killer, etc). So ZD’s question was, “Can someone who is not-Frum likewise be considered a Tzaddik for similar or bigger reasons even though he is not Frum?”