It wasn't reflected in the movie, but in the book Dudley was briefly shown to have learned to respect Harry... notably for saving his life during the Dementor attack. He stood and shook his hand and sheepishly, but genuinely said thanks.
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(I think it was book seven, when the Dursleys were escorted from the house before Harry's final departure.)
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(I think it was book seven, when the Dursleys were escorted from the house before Harry's final departure.)