Cuts of it's head one by one and used his burning hot club to seal the neck so no new heads can grow.
Hera had raised the Lernaean Hydra specifically to kill Heracles. She was upset by its defeat and put it in a place of honor among the stars as the constellation Hydra.
Heracles
For every head cut off, the hydra gows two more. To counteract this, Heracles burned each stump of a head.
By most accounts, Lerna was near one of the entrances to the Underworld and the Hydra was placed to guard it.In later accounts, the Hydra was raised by Hera specifically to kill Heracles, and it's placement was more incidental.
Lernean Hydra.
Hercules/Heracles killed the Nemean Lion and the Hydra.
The Lernean Hydra is killed by Heracles in his second of twelve labors. However why the Hydra is killed is never fully explained.
heracles fought him in a battle so heracles would be one but i also know that the hydra fought with him in battles
He fought a hydra, a lion, a horse, a cerberus, a crab and a pig.
He cut off its heads, but he had to burn them so they don't come back{he had help from his nephew]. After he killed it, he dipped his arrows in its blood so they are so poisonus that they can kill someone just by scratching them.
Hercules with the help of his nephew Iolau. However the fight may still be deemed fair as the Hydra had the aid of Cancer (the crab.) Through a complex series of later events it is the venom of the Hydra that eventually kills Hercules.
The hydra of Lake Lerna (called the Lernean Hydra). Killing her was one of Heracles' labors.