Which is the largest kaiju monster in the entire Godzilla series from 54-04?

On film, it's Biollante. It weighs a hefty 220,000 tons.

Source: link

In all media, it's Bagan, who weighs a whopping 280,000 tons!

Source: link

Poor Keizer Ghidorah only weighs a mere 100,000 tons.

Source: link

JD

keizer Ghidorah weights 100,000 and 140 feet tall. but then again Bagan is the largest kaiju and he weight 280,000 tons and 150 feet tall.
oh godzilla doesn't compare in size with these two.
godziila weights about 20,000 tons and 50 to 100 feet high

If you are talking about Height then its King Ghidorah because he is 150 meters tall(492.125984 feet). If you are talking about weight then its Biollante(100,000 metric tons).

Biollante.

I would say biolante I don't think I spelled that right but that's my guess

Biollante.

If you question about weight it's biollante, because she's 220,000 metric tons, but if you question about height it's kaizer ghidorah, because he's 150 meters tall what is taller than KG.

Biollante weight-wise, Keizer Ghidorah height-wise. I don't count Bagan because he has never had a finished film so no one knows for sure except from playing a video game.

Dogora, definitely. Dogora was hugely gigantic. He looked like he was able to swallow Tokyo.

I think Super Mecha Godzilla is the worst cause in the 1993 film Godzilla nearly got killed like Keizer Ghidorah in Godzilla Final Wars in 2004. Super Mechagodzilla 120 meters (393 feet) tall, weighs 150,000 metric tons (165,346 short tons), and can fly at speeds of up to Mach 1 in its standard form. Combined with the Garuda as Super Mechagodzilla, it weighs 150,482 metric tons (165,878 short tons), and can fly at speeds of up to Mach 2. Plus he has those cables that when he plumbed them into godzilla the first time godzilla was able to counter it but the second time he nearly died if it wasnt for Fire Rodan Godzilla would already be dead.