There are quite a few species that produce very large pitchers, and individuals that produce monster ones. For example, rafflesiana is not often credited for being a species that produces the largest pitchers, and most are fairly average. But the largest pitcher I've have ever seen was a raff. Rajah, merrilliana, sibuyanensis, sumatrana, truncata, even macrophylla and burbidgeae can produce very large pitchers.
In short, I doubt you could say that any one species produces the largest pitchers. There are many, and you can never discount a species which normally doesn't produce large pitchers producing an enormous one.