The muggles of the Harry Potter world rarely get a spotlight throughout the series although their bravery (or lack of) is commendable to say the least.
There is no shortness of courage and bravery within the world of Harry Potter, both in the films and books. Although bravery is subjective, there’s an untold bravery required to exist in this world, especially as someone who lacks magic.
The Dursley family in general carries less a sense of bravery rather than pure audacity so in the frame of “bravery,” this family of muggles is the least brave in the franchise, with their only bravery being to risk being so rude to wizards. Starting with Aunt Marge, clearly abuse and rudeness are traits innate to this family and she does not fall short in that category. After constant berating of Harry and the insults to his deceased parents, her short-lived cameo in Prisoner of Azkaban got her exactly what she deserved, getting blown up like a balloon.
Vernon isn’t brave, but is willing to risk magical retribution for his horrible treatment of Harry, beginning with physically keeping Harry locked in a room under the stairs, to the lengths he took to keep Harry away from Hogwarts all in Sorcerer’s Stone (or Philosopher’s).
Continuing on his high horse of pride and ego, Vernon then continues to try to keep Harry locked up, knowing the amount of powerful witches, wizards, and magical creatures that stood behind Harry. As a non-magic human with nothing but flesh and blood to protect him, it was a huge risk for Vernon to keep being a horrendous person who exists in a world of magic that could harm him, time and time again.
Dudley was easily unlikeable considering he was spoiled and vile toward Harry almost always. Over time, less blame is placed upon Dudley when the realization occurs that he was merely raised and conditioned under spoiled tendencies and his parents’ hate toward Harry and magic. Dudley carries his “bravery” to no surprise, by choosing to be a menace to someone who carries significantly more power than him – and the mending of their relationship later on in the series allows some grace to be held for him. Even though Harry saved his life and that was the only reason Dudley decided to stop hating him, maybe it’s because someone showed him genuine compassion for once.
The Prime Minister
Although the Prime Minister believed and knew that the wizarding world was real, he didn’t necessarily want anything to do with it. He was unfortunately roped into dealing with Cornelius Fudge at the Ministry of Magic and it’s fair to say that he buried his head in the sand about the wizarding world, so much so that he tried to convince himself that Fudge was a hallucination – but his bravery emerges by being a muggle overall graced with this knowledge. The Prime Minister more so has a forced bravery thrust upon him rather than self-generated but to know details of the wizarding world and having to act on those potential threats to human lives requires a sense of bravery that not everyone could have dealt with.
The campsite owner at the Quidditch World Cup, Mr. Roberts, also carried a sense of bravery forced upon him but it was more so obliviousness over anything else. In fact, had to be constantly Obliviated thanks to his suspicions about his new guests (the witches and wizards), and probably came out of the whole thing pretty dazed and confused when he was just trying to do his job as a groundskeeper. Still, props will be given to him in a false sense of bravery (or obliviousness) to allow the wizards their space for Quidditch as well as for the torment he and his family endured soon after by the Death Eaters in the riot.