Antiphates--king of the Laestrygones. He ate one of Odysseus' heralds, and destroyed all of Odysseus' fleet except for the vessel that Odysseus escapes on.
Otus & Ephialtes--inprisioned Ares in a bronze jar for 13 months
Enceladus--had serpents for legs-buried under Mt. Aetna
Euryton--guarded Geryon's cattle
Tityus--Attacked Leto and thus sentenced to Tartarus with an eagle continually devourering his liver