Yes, “giant squids” definitely exist. I have held the head of one in my hands and here is the interesting thing. They actually aren’t all that giant, and nor are they the biggest squid, nor the squid that can do the most damage. This is what they look like.
What giant squid do have are seriously long tentacles. Some of their tentacles stretch for more than 10 metres. So people hear about 12m or 14m squid they imagine the head of the squid to be the size of a minivan with moderately long tentacles. They have a mass of up to 275kgs. Not small by any stretch of the imagine, but hardly giant.
No, they are nowhere near as giant as the “collosal squid” (Mesonychoteuthis hamiltoni). These squid look like this:
As you will see, they have a giant mantle but very small tentacles. They are less than 10m in total length, but they have an adult mass of at least 495kgs. They are often eaten by sperm whales, and the beaks of collosal squid (which indicate an adult’s size) have been found inside the stomachs of sperm whales, indicating that some specimens weigh 600–700kgs.
I have been fortunate enough to hold in my hand the eye of the largest specimen ever recovered. That is the largest eye known to exist, and is a bit bigger than a dinner plate (40cms).
If you ever see images of sperm whales and they have scars all over them, you can probably imagine the fearsome fight the collosal squid put up to avoid being eaten. Scars like the sperm whale in the below image.