In the writings of HPL Cthulhu was defeated by ramming him with a fishing boat. In pop-Cthulhu Cthulhu is on an unimaginable power scale and the fishing boat would just bounce.
In the H. P. Lovecraft story the Call of Cthulhu, Cthulhu was rammed in the head by a steam-ship...and he instantly started regenerating. Like hitting a troll with a rock. So temporarily “defeated” by taking a steam-ship to the face. We should note that at the time the story was written, the steam-ship was the most powerful bit of water-borne technology invented by humans. The effect is different on modern readers from the original intent. Then it was meant to convey the horror that even our most powerful water-borne invention was only a split second reprieve, now it reads like “LOL, Cthulhu was taken out by a boat.” The ignored context matters.
Context now would be ramming Cthulu with the USS Nimitz and then having all of its reactors go super critical and explode on impact.
HPL wrote the story in the mid-1920s. The story "quotes" from the Sydney Bulletin for April 18, 1925. When "great Cthulhu slid greasily into the water and began to pursue with vast wave-raising strokes of cosmic potency" it was in pursuit of the
Alert, a "heavily armed steam yacht Alert of Dunedin, N. Z."
Here is a web page about an Australasian steam yacht of the same general era:
Ship specifications - Australian National Maritime Museum. Here is its Wikipedia page:
SY Ena - Wikipedia. Given that the 11-man crew of "the two-masted schooner
Emma" were able to take the Alert in a boarding action, I'm guessing the latter was comparable to the vessel on that web page.
The Ena displaces 76 tons; it's maximum speed is 12 knots. HMS Dreadnought, the famous battleship built in 1906, displaced 18,000 tons with a maximum speed of 21 knots. HMS Orion, built in 1910, displaced around 22,000 tons and also had a maximum speed of 21 knots. Another 5 years later the HMS Revenge displaced close to 30,000 tons with a maximum speed of 23 knots. And for purposes of comparison, the USS Nimitz displaces about 100,000 tons and has a speed of about 31 knots.
So no, to HPL and readers of his day Cthulhu being rammed by the
Alert was nothing liked being rammed by a giant warship. If we think of it in terms of contemporary fiction, it's in the same general ballpark as being hit by a semi-trailer or a tank travelling at full speed.