Though Harry has certainly grown up in unfortunate circumstances with the Dursleys and has suffered more than his fair share of abuse at their hands, the fact remains that he's still very fortunate in terms of finances and fame. Whether or he realizes it or not, this gives Harry a great deal of power to influence others. By comparing how Harry uses his fame and fortune to the ways in which other characters use theirs, Goblet of Fire suggests that while fame, fortune, and power don't automatically equate to good or evil, possessing fame or money means that a person much choose whether they'll actively use that power for good or evil.
While Harry, as the novel's protagonist, is undeniably a "good guy," there are also a number of indications that this status is a matter of choice. Whether Harry truly realizes it or not, he has a great deal of privilege--his parents left him a small fortune, and his most prized possessions are extremely valuable magical objects (his Invisibility Cloak, his Firebolt racing broom, and the Marauder's Map). However, rather than choose to use these items and his money for his own gain, Harry overwhelmingly chooses to use these objects to help others and shares his wealth with his friends. In this way, it's telling not just that Harry gives away the thousand Galleons that he wins in the Triwizard Tournament to Fred and George; more indicative of Harry's goodness is that he asks them to use part of the money to buy Ron new dress robes, something that he knows will ease Ron's way going forward (his current robes, which are secondhand and dated, made the debacle that was the Yule Ball especially humiliating for Ron). With this, Harry demonstrates that he understands how his wealth and power have the potential to help people, and that doing so is extremely fulfilling.
There are a number of characters that exist in contrast to Harry in this way, most notably Mr. Crouch and Ludo Bagman. Harry gets his first indication that Mr. Crouch isn't particularly caring when he notices that Mr. Crouch still doesn't know Percy Weasley's name, despite the fact that Percy has been working for Mr. Crouch for several months at the start of the novel. Later, Sirius tells Harry, Ron, and Hermione that Mr. Crouch has been a big and powerful name at the Ministry for a long time and, at the time of Voldemort's defeat, was poised to become Minister of Magic. He made his name putting Death Eaters behind bars after Voldemort's fall--including both Sirius and Mr. Crouch's own son, Barty Crouch. Sirius poignantly tells Harry that difficult times can bring out the best and the worst in people, and Voldemort's reign of terror brought out the worst in Mr. Crouch. Drunk on power, Crouch authorized the use of the Unforgivable Curses on suspected Death Eaters and put a number of people in the prison of Azkaban without trials. Sirius insists that it was a merciful act for Mr. Crouch to even give Barty Crouch a trial, even if his son ended up in Azkaban anyway. Even after it comes out that Barty Crouch didn't actually die in Azkaban--Mr. Crouch smuggled him out disguised as his wife and kept him under the Imperius Curse (mind control) for thirteen years--his actions illustrate how an individual can abuse their power and their prestige to forcibly get their way, even if, technically speaking, they're on the side of good.
Ludo Bagman, a former Quidditch player and the current head of the Department of Magical Games and Sports, also falls into this category of not technically bad, but not entirely good either. When Harry unwittingly ends up viewing Dumbledore's memories of several trials of suspected Death Eaters in his Pensieve (a bowl-like object that holds, shows, and allows people to re-experience memories), he learns that Bagman himself was suspected of passing information to the Death Eaters--but because of Bagman's fame as a Quidditch player, he wasn't convicted, and his trial appears to be more of a formality than an actual attempt to find wrongdoing. Both Crouch and Bagman, then, show Harry what he could do with his power should he choose to do so, and their reputations also make it clear that the line between "good guys" and "bad guys" isn't at all clear-cut: while both abuse their power in various ways and, in Bagman's case, have possible connections with Voldemort, Bagman is a beloved figure who manages to salvage his reputation while Crouch struggles to do either.
Taken together, the individuals that Harry meets over the course of his fourth year at Hogwarts show him clearly that humanity is more complex than the simple dichotomy of non-Death Eaters and Death Eaters, good and evil. Instead, by illustrating Harry early in his life and making it clear that he has the opportunity to abuse his fame and fortune if he so chooses, the novel suggests that good and evil aren't innate states of being. Instead, it suggests that a person becomes good or evil--or somewhere in between--through the choices they make and, in particular, how they choose to use or abuse the privileges they're born with.
Good, Evil, Power, and Choice ThemeTracker
Good, Evil, Power, and Choice Quotes in Harry Potter and the Goblet of Fire
"Oh really," said Mr. Weasley in exasperation, handing the paper to Percy. "Nobody was hurt. What was I supposed to say? Rumors that several bodies were removed from the woods...well, there certainly will be rumors now that she's printed that."
"It's all in Hogwarts: A History. Though, of course, that book's not entirely reliable. A Revised History of Hogwarts would be a more accurate title. Or A Highly Biased and Selective History of Hogwarts, Which Glosses Over the Nastier Aspects of the School."
"What are you on about?" said Ron, though Harry thought he knew what was coming.
"House-elves!" said Hermione, her eyes flashing. "Not once, in over a thousand pages, does Hogwarts: A History mention that we are all colluding in the oppression of a hundred slaves!"
"Oh Harry, isn't it obvious?" Hermione said despairingly. "He's jealous!"
"Jealous?" Harry said incredulously. "Jealous of what? He wants to make a prat of himself in front of the whole school, does he?"
"Look," said Hermione patiently, "it's always you who gets all the attention, you know it is. I know it's not your fault," she added quickly, seeing Harry open his mouth furiously. "I know you don't ask for it...but--well--Ron's got all those brothers to compete against at home, and you're his best friend, and you're really famous--he's always shunted to one side whenever people see you, and he puts up with it, and he never mentions it, but I suppose this is just one time too many..."
"--and reading between the lines of that Skeeter woman's article last month, Moody was attacked the night before he started at Hogwarts. Yes, I know she says it was another false alarm," Sirius said hastily, seeing Harry about to speak, "but I don't think so, somehow. I think someone tried to stop him from getting to Hogwarts. I think someone knew their job would be a lot more difficult with him around. And no one's going to look into it too closely; Mad-Eye's heard intruders a bit too often."
"Why are you telling me?" he asked.
Harry looked at him in disbelief. He was sure Cedric wouldn't have asked that if he had seen the dragons himself. Harry wouldn't have let his worst enemy face those monsters unprepared--well, perhaps Malfoy or Snape...
"It's just...fair, isn't it?" he said to Cedric. "We all know now...we're on an even footing, aren't we?"
"He's from Durmstrang!" spat Ron. "He's competing against Harry! Against Hogwarts! You--you're--" Ron was obviously casting around for words strong enough to describe Hermione's crime, "fraternizing with the enemy, that's what you're doing!"
"What did you bring her for?"
"Fleur didn't turn up, I couldn't leave her," Harry panted.
"Harry, you prat," said Ron, "you didn't take that song thing seriously, did you? Dumbledore wouldn't have let any of us drown!"
"The song said--"
"It was only to make sure you got back inside the time limit!" said Ron. "I hope you didn't waste time down there acting the hero!"
Harry felt both stupid and annoyed. It was all very well for Ron; he'd been asleep, he hadn't felt how eerie it was down in the lake, surrounded by spear-carrying merpeople who'd looked more than capable of murder.
"Yes," said Hermione in a heated voice, "he sacked her, just because she hadn't stayed in her tent and let herself get trampled--"
"Hermione, will you give it a rest with the elf!" said Ron.
Sirius shook his head and said, "She's got the measure of Crouch better than you have, Ron. If you want to know what a man's like, take a good look at how he treats his inferiors, not his equals."
"Crouch let his son off? I thought you had the measure of him, Hermione! Anything that threatened to tarnish his reputation had to go; he had dedicated his whole life to becoming Minister of Magic. You saw him dismiss a devoted house-elf because she associated him with the Dark Mark again--doesn't that tell you what he's like? Crouch's fatherly affection stretched just far enough to give his son a trial, and by all accounts, it wasn't much more than an excuse for Crouch to show how much he hated the boy...then he sent him straight to Azkaban."
Dumbledore gave Harry a very sharp look. "Has Neville never told you why he has been brought up by his grandmother?" he said.
Harry shook his head, wondering, as he did so, how he could have failed to ask Neville this, in almost four years of knowing him.
"And I answer myself, perhaps they believed a still greater power could exist, one that could vanquish even Lord Voldemort...perhaps they now pay allegiance to another...perhaps that champion of commoners, of Mudbloods and Muggles, Albus Dumbledore?"
"For heaven's sake, Dumbledore--the boy was full of some crackpot story at the end of last year too--his tales are getting taller, and you're still swallowing them--the boy can talk to snakes, Dumbledore, and you think he's trustworthy?"
"You fool!" Professor McGonagall cried. "Cedric Diggory! Mr. Crouch! These deaths were not the random work of a lunatic!"
"The second step you must take--and at once," Dumbledore pressed on, "is to send envoys to the giants."
"Envoys to the giants?" Fudge shrieked, finding his tongue again. "What madness is this?"
"Extend the hand of friendship, now, before it is too late," said Dumbledore, "or Voldemort will persuade them, as he did before, that he alone among wizards will give them their rights and their freedom!"
"The Ministry of Magic," Dumbledore continued, "does not wish me to tell you this. It is possible that some of your parents will be horrified that I have done so--either because they will not believe that Lord Voldemort has returned, or because they think I should not tell you so, young as you are. It is my belief, however, that the truth is generally preferable to lies, and that any attempt to pretend that Cedric died as a result of an accident, or some sort of blunder of his own, is an insult to his memory."