When Dumbledore realised his rightful path
It came as a surprise to many people, Harry included, that Dumbledore had once been close friends with the powerful Dark wizard Gellert Grindelwald and even shared some of his beliefs to an extent. It seemed completely at odds with the Dumbledore we knew and loved, and yet when more of the sad tale of his past was uncovered, it wasn’t so far removed after all.
Only after the tragic death of his little sister Ariana, during a duel between Albus, Aberforth and Grindelwald, did Dumbledore realise what he was becoming. His actions during the years afterwards show that he spent the rest of his life trying to make up for what had happened. It seems that his love for his little sister and the guilt he felt over her loss played a big part in that, even though Aberforth never fully forgave him.
When Mrs Weasley took on Bellatrix
Molly, the matriarch of the beloved Weasley clan, could never be dubbed a shrinking violet – seeing as her fury was the only energy source in the world that seemed to stop Fred and George in their tracks. And yet her temper was usually born out of love and worry for her family, something we caught in awful detail when a Boggart revealed her greatest fear was seeing the family all dead.
This love may have hindered her in the face of a Boggart, but it also transcended into immense power when she defended Ginny from Bellatrix during the Battle of Hogwarts, giving us the immortal line ‘Not my daughter, you bitch!’ Despite facing her worst fear already that night (Fred’s death), her love for Ginny galvanised her into action and was one of the only things powerful enough to destroy the stubbornly persistent Bellatrix once and for all.
When it saved Harry’s life
Harry’s story truly started the night Voldemort broke into the Potters’ home in Godric’s Hollow. James died trying to protect his wife and child, while Lily sacrificed herself even when Voldemort told her to step aside. As Dumbledore realised, and Voldemort didn’t understand at the time, her sacrifice that night gave Harry a unique protection that would only break when he was 17.
When Harry chose to sacrifice himself
Lily Potter could always give Harry the power he needed, even in death. With Harry under the belief he must die at Voldemort’s hand, he found himself in possession of the fabled Resurrection Stone, so his parents, Remus and Sirius could be with him as he sealed his fate. With these reminders of his life surrounding him, and the sight of his mother’s eyes, he had the strength to finally make the ultimate sacrifice.
When Narcissa lied to Voldemort
Although never a Death Eater, Narcissa Malfoy was always lurking in the background, supporting Lucius and Draco from the shadows. For a while, Narcissa’s intentions were largely ambiguous, until Voldemort sent her to check if Harry had finally been killed.
Upon discovering Harry was still alive, instead of giving him up she asked him a question: ‘Is Draco alive?’ Hearing that he was, she lied to the Dark Lord about Harry – revealing that any allegiance she might have had to Voldemort would never match the love she had for her son.
As Dumbledore went to such great pains to explain, this was one of Tom Riddle’s greatest failings; he could never understand the power of love.