For Handel, “Hercules” represented its own kind of trauma. The work flopped so badly at its London premiere in 1744 that he withdrew it after two performances and ran a mortified announcement in the press announcing a premature end to his concert season. Sunday’s performance, featuring the luminous Clarion Choir and a strong cast of soloists, made a persuasive case for the piece as one of Handel’s most musically and psychologically brilliant creations. It’s also easy to see what alienated Handel’s contemporaries. Even today, “Hercules” feels strikingly modern, with flights of chromatic daring and a compassionate gaze on mental torment that pierces through the moralizing veneer of 18th-century English spectacle.