achillean

from The Century Dictionary.

• Of, resembling, or belonging to Achilles, the hero in the war against Troy, noted for his valor, swiftness of foot, etc., but especially for unrelenting wrath; hence, valiant, swift, unrelenting, etc.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Resembling Achilles, the hero of the Iliad; invincible.