Harry's drive and natural talent had gotten him far during the last year and a half. If he had more time, he would probably be able to beat the Dark Lord despite Riddle's experience and ritualistic advantage. Testament to that, Harry had held his own for nearly ten minutes, and everyone else that came with the Dark Lord perished during the fight. Yet Harry couldn't claim all the credit here, Voldemort had used devastating magic freely, without any care for his minions slaying more than one in the crossfire. When Harry was finally struck by the killing curse for the second time, he simply smiled as the green light hit him in the chest.