Harry potter
A proverbial savior – the boy who survived.
He never thought he was so powerful
One, who survived due to his mother's protective spell, is not powerful at all.
At least, that's what Harry thought.
Relying on the magic discovered in the forbidden book area with Hermione, he safely returned from the future to the past under Voldemort's death curse, in order to kill Tom. Riddle, but mistakenly returned to 1926.
Seeing a still innocent little life in his arms, Harry hesitated
"... Next time... Next time..."
Not really whitening Voldemort, not darkening Dumbledore, the character is slightly out of shape (right?)