Herc's strength and immortality can and have been taken away from him in the past.
He's also blessed with other handy abilities like immortality, invulnerability and enhanced speed and healing. Thanks to his divine origins, Herc has incredible physical strength - enough to make him a match for Thor and even hold his own in battle against the Hulk.
The Greek myths paint Hercules as far stronger and more skilled in battle than any mortal, and that's certainly true for the Marvel version.
