Dionaea 'B52' has for a long time held the record for largest, but some of the new giant forms may surpass even it.
For sheer size, N. bicalcarata is definitely the biggest plant, but pitcher wise, in general rajah has the largest traps. The other new species may certainly occasionally put out pitchers that outdo rajah, but for pitcher size on average nothing yet beats it.
With Sarracenia, flava rugelii holds the record right now, with some plants having been recorded at more than 4' tall, but leucophylla and x moorei are definitely close.
Heliamphora I can't really speak for, but I know ionasii and tatei are both famed for size
P. gigantea is probably largest by mass, but longifolia or vallisneriifolia have far longer leaves.
D. gigantea and regia, by mass, may be the largest, but D. erythrogyne is the longest, with climbing stems up to 10' in cases.
The largest bladderwort species I've seen yet may be U. floridana, as I've seen pictures of plants easily having branches of 7 or 8 feet before. For bladder size, humboldtii and arnhemica are both close, and for leaves longifolia probably does have the longest on average, but U. cornigera can have some massive lamina.