When giant squid are small, babies and juveniles, they can have many, many predators. Mostly various kinds of fishes, deep sea fishes. However, once giant squid get beyond a certain size, they have outgrown the size of most of their potential predators. So when they are adults, about the only predator that we know of for giant squid is the sperm whale. And sperm whales get up to be 40-50 feet in length, but they weigh 30-40 tons. So even though a giant squid is huge, it is not big enough to escape or to fight with a sperm whale. I would say the sperm whale always wins.
