If two heads are better than one, then clearly three heads are better still. And here’s all the proof you need.
Ghidrah (yeah, I’m old school) not only had one of best entrances of any monster, but was so awesome that he was felled by the Galactus Effect. This stipulates that a perfectly conceived, seemingly unbeatable menace is diminished by subsequent appearances since they then need to be defeated again each time they show up. Eventually their luster is largely obliterated. The Borg also fall into this category.
Ghidrah was instantly diminished in Monster X, despite being portrayed as a literal world-destroyer, because it now took two monsters to defeat him as opposed to Toho’s entire Big Three. After taking a gang thrashing in Destroy All Monsters, Ghidrah was never the same, and basically coasted along on his reputation. By the Heisei series Godzilla was being portrayed basically as completely unbeatable, so that the now King Ghidorah not only couldn’t take the Big G just by himself in a straight fight, but couldn’t even do it when augmented into Mecha-King Ghirdorah.
I’ll always remember him as he was the first time, though. Hail to the King.