Which Hekatoncheires was also known as Aegaeon?

The Hekatoncheire also known as Aegaeon was Briareus. Homer’s Iliad says Briareus is the name used by the gods, while mortals call him Aegaeon.

Briareus was one of the three Hekatoncheires, or Hundred-Handers, monstrous children of Gaia and Uranus. Each had fifty heads and one hundred arms; the other two were Cottus and Gyges. In Hesiod’s Theogony, the brothers were imprisoned by Uranus and later helped Zeus defeat the Titans.

The Homeric Briareus is a powerful ally of Zeus. When Hera, Poseidon, and Athena attempted to bind Zeus, the sea goddess Thetis summoned Briareus to Olympus, discouraging the rebels. Hesiod also describes him as favored by the gods and married to Cymopolea, a daughter of Poseidon.

Some later traditions treat Aegaeon as a sea-associated monster or even as an opponent of the Olympians. Those variations do not change the standard identification in this question: Briareus and Aegaeon are alternate names for the Hekatoncheire.