There's some debate about who the clear hero of the Harry Potter franchise would be. The titular character, of course, has a claim to the title, but so does Hermione (without whom, Harry would be long dead), Dumbledore himself (despite some manipulations), even Minerva McGonagall (who is a clear fan-favorite). However, there are some heroes who also get very little credit for all the good they do in this world.
Whether it is villainous characters who have heroic moments, minor characters who have a surprisingly big impact on the story, or straight-up heroes who just don't get enough credit, these are the unsung good guys of the Harry Potter franchise.
Regulus Black - Stole A Horcrux
Regulus Black is not actually seen alive in the series, and is only mentioned in passing. Sirius mentions him when talking about his family, and later on, the Golden Trio discover that Regulus turned on Voldemort and the Death Eaters later in life.
Despite the fact that he succeeded in discovering Voldemort had created Horcruxes, stealing one of them, and defecting as a Death Eater, Regulus is largely overlooked by the fandom. This may be because his actions didn't help anyone - Dumbledore and Harry would have found the locket anyway, and Regulus wasn't able to destroy it - or because of his history as a Death Eater, but he's still a hero... of sorts.
Viktor Krum - Pointed Harry To The Deathly Hallows
Krum is a major player in the franchise only in The Goblet of Fire, and his main contribution to the series is often seen as sparking jealousy between Hermione and Ron. However, he reappears at Bill and Fleur's wedding, where he becomes angry at seeing Xenophilius Lovegood wearing the symbol of the Deathly Hallows, and tells Harry about it.
This moment is the one that connects Lovegood and the Deathly Hallows in Harry's mind - and as soon as he sees the mark later, he immediately knows that Xenophilius is the one to ask about it. Had Krum not mentioned this at the wedding, the Golden Trio may never have found out what they did - which would have changed the entire ending, as Harry wouldn't understand the resurrection stone, or the Elder Wand.
Florean Fortescue - Gave Harry Some Much-Needed Love
Florean Fortescue barely appears in the movies, but in the books, he becomes a real friend to Harry. The owner of the Diagon Alley ice cream parlor, he provides Harry with a place to work on homework when staying at the Leaky Cauldron. More than that, he also gives him help with his work, and free ice cream.
It may not seem like much, but for someone like Harry, this would have been incredible. A kind parental figure, happy to indulge and help with homework, is something he would not have experienced at home - and while it's a small thing, it's a vital one.
Colin Creevey - Helped Hermione Figure Out The Basilisk
Colin Creevey exists largely as a comic annoyance, and later, a tragic footnote when he dies at the Battle of Hogwarts. However, as one of the students who was first petrified by the Basilisk in the Chamber of Secrets, he was instrumental in helping Hermione (and in turn, Harry) figure out what was harming the students.
He was petrified because he was looking through his camera - and that (along with Justin and Nearly Headless Nick) would have been enough to set Hermione on the right track. Given that Hermione was petrified soon after, saved only by the use of a mirror, he could even be credited in part with saving her life. Had he not been petrified through his camera, she may not have figured it out and used the mirror.
Filius Flitwick - At The Battle Of Hogwarts
Charms Professor Filius Flitwick just doesn't get enough credit, despite being an active participant in all the major battles of the series. He fought against Voldemort in both Wizarding Wars, subtly undermined Umbridge along with the other teachers, fought in the Battle of the Astronomy Tower, and fought in the Battle of Hogwarts.
Compared to many others, though, Flitwick is often overlooked. This may be because he was not a member of the Order of the Phoenix, although it's not clear why this is.
Kingsley Shacklebolt - Warned The Golden Trio At The Wedding
Kingsley Shacklebolt is, admittedly, a recognized member of the Order of the Phoenix, and even becomes Minister of Magic after the Second Wizarding War. In many ways, he is seen as a true hero of the franchise, but one of his most impactful actions is often forgotten - warning the wedding guests so the Golden Trio could flee.
If not for this warning, Harry, Hermione, and Ron may well have been captured by the Death Eaters early on, and that would mean Voldemort's triumph. In many ways, this was one of the few actions that could make or break the plot, and as such, it deserves more attention in the fandom.
Arabella Figg - Lied To The Court For Harry
Harry's Squib neighbor, Arabella Figg, only has a small part in the franchise. She looks after Harry sometimes when he is a child, but she also vouches for him in his trial for the use of underage magic. She stands up to give testimony in front of a full Wizengamot, despite how terrifying this was - made more so by the fact that she lied. She could not see Dementors, as a Squib, but claimed she could to help Harry win his case.
Of course, Harry did truthfully fight off Dementors, so her lie was a small one, which may be why it doesn't get more attention. But had Mrs. Figg not been a witness, the case may not have gone in Harry's favor - and had he been expelled, it would have changed everything - and likely for the worse.
Lee Jordan - Hosted Potterwatch
Lee Jordan, Fred and George Weasley's friend and Quidditch commentator at Hogwarts, is usually seen as just some comic relief in Quidditch matches, but he's more of a hero than many think. During the Second Wizarding War, Lee hosts the Potterwatch broadcast, rallying the resistance and offering helpful information.
This may be overlooked largely because it is one of the book elements that is heavily downplayed in the movies. There is a radio that the Golden Trio listen to in The Deathly Hallows, and at one point this includes a broadcast list of missing witches and wizards. However, the bulk of what Potterwatch does isn't seen - and it is this that makes Lee so much more heroic.
Kreacher - Not Just A Bad Elf
Of the named House Elves in the Harry Potter franchise, fans love Dobby as a tragic hero, but often forget about Kreacher - or even see him as a villain. The Black House Elf definitely does have some villainous qualities, and his part in the death of Sirius should not be underplayed, but his actions in the end were clearly heroic.
When treated with respect by Harry, Hermione, and Ron, he took good care of them, cooking and cleaning for them while they stayed at Grimmauld Place. He told them about the locket, and who took it, allowing them to find it. In the books, he also fights in the Battle of Hogwarts, leading the Hogwarts House Elves to battle - an effort that would have had a powerful impact, given the magic the House Elves have.
Narcissa Malfoy - Saves Harry
Narcissa Malfoy is usually considered a villain in the Harry Potter franchise - a Malfoy, a Death Eater, and a woman whose odious beliefs seem clear from the start. Despite all this, though, she was something of a hero in the end.
By the Battle of Hogwarts, the Malfoys had turned on Voldemort, and wished only to leave the Death Eaters with their son. So, when Harry was lying "dead" in the Forbidden Forest, Narcissa was the first to check on him - and to lie to the Dark Lord about his state. Had she not done this, Voldemort would have presumably murdered Harry there and then. Her motives may have been selfish, but Narcissa did save Harry's life, which makes her at least some level of hero.