Charged by Hera with guarding the Golden Apples of the Hesperides, Ladon was eventually defeated by Hercules.
Ladon
For stealing fire from the gods and giving it the mortals, the Titan Prometheus was punished by having his ever-regenerating liver eaten daily by the Caucasian Eagle ("caucasian" here meaning "of the Caucasus Mountains", where the punishment took place).
The Eagle itself has two different origins: a flesh-and-blood monster offspring of Typhon and Echidna, or a bronze automaton created by the smith-god Hephaestus.
A fire-breathing monster that terrorized Lycia, the Chimera was the sister of many other infamous beasts, like the Sphinx, Cerberus, and Hydra. She was also the cousin of Pegasus, who ultimately aided Bellerophon in killing the Chimera.
So poisonous it's tracks were deadly, and having the ability to regrow two heads for every one destroyed (although one was immortal), the Hydra was a formidable monster that lived in the swamp near Lernae. To make matters worse for any would-be monster slayers, the Hydra had an ally, a giant crab.
Despite the seemingly impossible odds, Hercules and his nephew Iolaos were able to slay the monsters (and safely buried the immortal Hydra head under a rock). Although unable to kill the heroes, Hera rewarded the Hydra and Crab for their efforts by placing them in the heavens as the constellations Hydra and Cancer.
An ally of the Lernaean Hydra, Carcinus rushed to the she-serpent's aid when the hero Hercules attacked her, but was soon crushed. Carcinus' history is unknown -- we aren't told who he's related to (he may very well just be a normal crab), if he was acquainted with Hera like most monsters that fought Heracles, or why exactly he comes to the Hydra's aid.
An unnamed* child of Echidna, this Giant fought alongside the Titans against the Gods, though was ultimately killed by Ares. This "masterpiece", as Nonnus put it, would catch birds in his beard for dinner.
*Echidnades ("of Echidna's lineage") is more of a description than an actual name
Like many of Typhon and Echidna's brood, the Nemean Lion was raised by Hera and set loose upon some poor village, then was later placed in the stars by the goddess after it was killed by the hero Hercules.
The Nemean Lion's hide was impervious to all weapons, and the monster had to be strangled to death (still no easy task, as Hercules lost a finger during the fight in one account). Not letting a good thing go to waste, Hercules wore the lion's skin as armor, which became one of the hero's trademark attributes.
