If there's a main hero in Harry Potter, of course it's the titular character himself. While the series juggles multiple storylines, at its core it's about Harry's transformation from The Boy Who Lived to the Chosen One who defeats Lord Voldemort and saves the entire wizarding world.
Harry performs multiple impressive feats along the way — but he also has plenty of help. His friends are there in nearly every dangerous situation, and sometimes it's their skills, knowledge, and ideas that facilitate Harry's victory. Sometimes, it could even be said that without them, Harry wouldn't have survived to see his next battle with the dark side.
The Horcrux Hunt In The Deathly Hallows
The plot of Deathly Hallows looks very different to the rest of the series. Instead of being structured around another year at Hogwarts, it sees Harry, Ron and Hermione go on the run as they attempt to track down and defeat the Horcruxes keeping Lord Voldemort alive.
But with little to go on, a lot of the Horcrux hunt involves sitting in a tent. Harry probably couldn't have survived even that alone. It's Hermione who steals and makes food–she also packs all the supplies, providing practical items like Essence of Dittany that Harry would've never thought to bring. If he'd had it his way and gone on his mission alone, there's a chance Harry might have just faced an undignified death from something like an infected wound in the forest.
Reaching The Final Room At The End Of The Sorcerer's Stone
Harry's instincts are one of his greatest strengths and help him figure out the mystery of the Philosopher's Stone in the first place. However, the obstacles to actually retrieve it required other skills that Harry lacked, such as strategy and logical deduction.
Thankfully, he had two friends who excelled in these areas. It's Ron who plots their victory on McGonagall's transfigured chessboard, and Hermione who solves the riddle to separate the right potions from the poisons. It's lucky that the trio's abilities complement each other so well — Harry is keen to forge through the defenses on his own, which wouldn't have ended well.
Getting Out Of Xenophilius Lovegood's House Alive
It's lucky Harry has Hermione around, because it's her idea to visit Xenophilius Lovegood in the first place. If they hadn't gone, Harry would never have heard more about the Deathly Hallows, never found out enough about the Elder Wand to realize he's its true master, and potentially would have never defeated Lord Voldemort at all.
Although the trip is useful, it was not without risk. When Xenophilius summons the Death Eaters, it's thanks to Hermione (again) that the trio escapes. She lets the Death Eaters confirm Xenophilius' story is true (so they don't blame him) before they Apparate away. It's a twist of genius that Harry's more than capable of but, being Harry, he would likely have tried to fight his way out and save Xenophilius instead.
Retrieving The Sword Of Gryffindor
Harry has countless near-death experiences in Deathly Hallows. One of the scariest occurs in the forest when he follows a doe Patronus (sent, unbeknownst to him, by Snape) to the Sword of Gryffindor in a frozen pond. In a typically reckless move, Harry blasts a hole in the ice and dives in, only for the Horcrux he's wearing to try to kill him.
Without intervention, there's no way Harry could have survived this incident. The Horcrux in question was an incredibly powerful object that certainly wouldn't have stopped fighting until Harry drowned. Fortunately, Ron finds him in the nick of time and pulls him to safety.
Getting Out Of The Chamber Of Secrets
From a young age, Harry is capable of holding his nerve in situations that would terrify most grown adults. In his second year at Hogwarts, Harry makes the brave decision to descend into the Chamber of Secrets to save Ginny Weasley, only to be confronted by the memory of Tom Riddle and the Basilisk.
Considering he was only 12-years-old at the time, Harry does an impressive job of standing up to both. However, his magic is nowhere near developed enough to defeat a Basilisk. When Fawkes arrives in the Chamber on Dumbledore's behalf bearing the Sorting Hat and Sword of Gryffindor, he's finally supplied with a weapon to kill the Basilisk, and the Phoenix tears to heal his wound. It's a miracle, saving not only himself but Ginny from almost certain death.
Escaping The Ministry Of Magic
The plan for the trio to break into the Ministry of Magic was a group effort. Over the course of a month, they carefully plot out how to retrieve Slytherin's locket from Dolores Umbridge — but none of them account for what to do if they're caught.
Obviously, they're caught. When Yaxley – a Death Eater working for the Ministry — realizes who they are, he latches on to Hermione as they're escaping. Harry is completely oblivious to this, even once they arrive at Grimmauld Place, but Hermione Apparates them away, knowing their hiding place is compromised. Harry would have likely reached the same conclusion with time, but by then it could have been too late.
Surviving Godric's Hollow
It's not surprising that Harry feels so strongly about visiting Godric's Hollow. Not only is it his birthplace, but it's where he lost both his parents and Voldemort met his first death (of sorts). After spending months convincing Hermione, their plans go awry when — in one of the most disturbing moments of the entire Harry Potter series — Bathilda Bagshot is revealed to be Nagini in disguise.
Having ventured upstairs alone with Bathilda, Harry is bitten and constricted by the snake. He's freed just in time, courtesy of a few curses from Hermione. While it's Harry who ultimately gets them out of Godric's Hollow, without Hermione he'd be trapped until Voldemort's arrival — and with several Horcruxes undestroyed at that point, it's doubtful Harry would have won that fight.
"Winning" The Triwizard Tournament
One of the key plot points in Goblet of Fire is the fact Harry couldn't have won the Triwizard Tournament without help. Barty Crouch Jr. (pretending to be Mad-Eye Moody) manipulates Harry's performance in every task, all to get him to the graveyard for Voldemort's reincarnation.
Harry is given the idea of flying in the first task, and Hermione teaches him how to summon his broom. Crouch prompts Dobby to give Harry Gillyweed to survive the lake in the second task and is on hand to help him navigate any challenging obstacles in the third task. Defence Against the Dark Arts is Harry's greatest strength, so he likely would have performed at least okay without interference, but it's a tall order to expect a 14-year-old to emerge unscathed otherwise.
Escaping Malfoy Manor
The mess at Malfoy Manor is completely on Harry. Caught up in the moment, he accidentally says Voldemort's name, triggering the Taboo that summons Snatchers to their tent. The incident would've escalated even sooner without Hermione, who responds quickly and jinxes Harry to be unrecognisable.
But even then, Harry still needs more help. After shouting into Sirius' old two-way mirror, Harry inadvertently summons Dobby. The house-elf manages to save them all, giving his life in the process. It's yet another loss for which Harry feels incredibly guilty, but without Dobby multiple lives (including Harry's) would have been lost that day.
Getting Out Of The Department Of Mysteries
Of all the things Harry feels guilty for, the Department of Mysteries ranks pretty high. In order to lure Harry to the Hall of Prophecies, Voldemort relies on Harry's "saving people" complex and puts a false vision into his mind that shows Sirius being held hostage.
Rushing off to save him, Harry and his friends are put in severe danger when they are confronted by Death Eaters. It's only when the Order and Dumbledore arrive that the tides of battle change for good. Harry loses Sirius that day — something he struggles with for a long time after — but if the adults hadn't got involved for once, or if Harry had gone to the Ministry alone, the damage could have been even worse.