Otus - Two sons of POSEIDON and Iphimedeia, EPHIALTES and OTUS (known jointly as the ALOADAE) were big lads. Even at the age of nine they were nine fathoms tall and nine cubits wide. So yes — they were TITANS.
They planned to steal away HERA and ARTEMIS, and to get a bit of kidnapping practice they abducted ARES and kept him in a bronze pot for thirteen months. If they could do that they could do anything.
HERMES eventually rescued him, but we don't suppose he was in any hurry. Then APOLLO stormed in and used them for a bit of archery practice. They both tried to retaliate by hurling their javelins at the first thing they saw, which happened to be a doe running between them. The doe smartly sidestepped and they hit each other.
These hits were fatal.
Their strategy has all the hallmarks of an ARTEMIS counter-plot. They had to go to hell of course, where they were tied to a column with serpents and humiliated by owls hooting at them. (godchecker.com)
Antaeus - A somewhat massive son of POSEIDON and GAIA, he mooched about in the Libyan Desert eating lions. He also killed travellers, because he collected skulls. We all need a hobby. ANTAEUS was hoping to collect enough to build a skull temple dedicated to his father.
HERACLES came across him while travelling to the Garden of the HESPERIDES and a fight ensued. ANTAEUS found his rib-crushing technique didn't work, being slammed to the ground three times in a row. HERACLES in turn was astonished to find his trusty body slams had no effect. ANTAEUS just came bouncing back.
GAIA was sending her power through Earthly contact, and whenever he touched the ground her son became stronger. So HERACLES went for the final submission by lifting the giant off his feet and throttling him in mid-air. (godchecker.com)
Enceladus - "Trumpeter to Arms" - one of the Gigantes, the enormous children of Gaia (Earth) fertilized by the blood of castrated Ouranos. With the other Gigantes, Enceladus appeared in one particular region—either Phlegra, the "burning plain" in Thrace, or Pallene.
Like the other Gigantes, Enceladus had serpent-like lower limbs, "with the scales of dragons for feet" as Bibliotheke states, though this convention was not invariably followed in pictorial representations.
During the battle between the Gigantes and the Olympian gods, Enceladus was disabled by a spear thrown by the goddess Athena. He was buried on the island of Sicily, under Mount Etna. The volcanic fires of Etna were said to be the breath of Enceladus, and its tremors to be caused by him rolling his injured side beneath the mountain. In Greece, an earthquake is still often called a "strike of Enceladus". (Wiki)
Tityos - a Phokian giant who assaulted the goddess Leto as she was on her way to Delphoi. Her son Apollon came to the rescue and despatched the giant with his arrows and golden sword.
As further punishment for the crime, Tityos was condemned to eternal torment in the underworld. There he was staked to the ground and two vultures set to feed on his ever regenerating liver.
His name might be derived from the Greek word tisis, meaning "he who suffers retribution." Alternatively Tityos may be connected with the Tityroi, a Boiotian name for flute-playing satyrs. In this guise he resembles another of Apollon's opponents, Marsyas. Certain elements of his story also closely resemble those of the Boiotian giant Orion and the Titan Prometheus. (theoi.com)