ほとんど

ほとんど means "almost", "almost all". Before a verb it says the action is nearly complete; before a noun it takes の and means "most".

• × ほとんど人 → ほとんどの人

With a negative

Before a negative, ほとんど means "hardly", "almost not at all".

The の changes what the negative covers. With ほとんどの on a noun, the sentence is about most of the people or things, and they did not do it.

ほとんど or 全然

ぜんぜん全然 with a negative is "not at all", with nothing left over. ほとんど leaves a little. ほぼ is close to positive ほとんど, "nearly", and sounds a little more written.