The cursed reincarnated heir

Darion Valtherion, heir to a powerful empire, was always a disappointment to his father, the invincible swordmaster, unable to match his prowess. Despite training tirelessly, he was always defeated by any soldier, and his life was one of constant humiliation. Betrayed and killed by assassins at age 23, Darion is reincarnated at age 18, but discovers that he is cursed: he will never be able to improve his swordsmanship.