Maybe it's because the victim had some special protection or magical ability that blocked it.
It could be that Draco didn't cast the spell correctly or with enough power. Or perhaps there was some external interference messing up the magic.
In the world of fanfic, it's a complex matter. From one perspective, using Crucio goes against Harry Potter's moral code in the original series. He is a hero who stands against the Dark Arts. However, in fanfic, authors might explore 'what - if' scenarios. But still, it's not an ethical act as Crucio is an unforgivable curse that causes extreme pain.
Draco may use Crucio on Harry due to his own insecurities. He might feel overshadowed by Harry all the time. His family's expectations to uphold their pure - blood superiority could also play a role. He could think that by using Crucio on Harry, he can assert his power and show that he's not to be trifled with. It could also be that he's caught up in the moment of a heated argument or rivalry and loses his temper completely.
Using Crucio on Harry would completely transform their relationship. Harry would be traumatized by the experience, and his view of Draco would be forever tainted. He'd see Draco as a heartless bully who is willing to use the darkest of magic. Draco, by doing this, has put himself in a position where any potential for friendship or even a civil relationship is gone. It would be the start of a long - running enmity, with the memory of the Crucio spell always lingering between them, fueling their animosity.
He could lose the trust of his friends. In the Harry Potter world, his friends know him as a good person. Using Crucio would shock them and make them question his integrity.
In the world of fanfiction, it's a complex matter. From one perspective, it's not ethical as Crucio is an Unforgivable Curse in the Harry Potter universe. It causes intense pain and is considered dark magic. However, in the realm of fanfiction, authors might explore different scenarios where Harry is forced into using it out of desperation or is under the influence of dark forces, which can be seen as a way to delve deeper into his character and the moral gray areas.
Well, I really like 'All Our Secrets Laid Bare'. In this fanfic, Draco's character development is amazing. It shows how he copes with the changing situations in the wizarding world. 'Away Childish Things' is also a great choice. It has a unique take on Draco's story, showing his growth from a spoiled brat to a more complex character. Then there's 'The Manuscript' which has an intriguing plot involving Draco and some long - lost magic secrets.
One possible consequence could be a moral breakdown within Harry himself. He's always been against dark magic, so using Crucio might make him question his own values. Another consequence could be alienation from his friends and allies. They would likely be shocked and appalled that he resorted to such a cruel curse.
I also recall a fanfic titled 'Lily and Draco: A Different Path'. This one takes a more adventurous turn. It's set in an alternate universe where Draco and Lily are forced to work together on a secret mission. As they face various challenges, they learn to understand and respect each other more. The author does a great job of portraying Draco's growth as he is exposed to Lily's Gryffindor qualities.
A possible plotline could be that Draco, out of curiosity, starts to research Harry Potter's mother. As he delves deeper, he finds out about her selfless love and her powerful magic. This makes him question his own values and beliefs, leading to a transformation in his character.
A good one is 'The Lightning on the Wave'. It offers a different perspective on Draco and Harry's relationship. The author does a wonderful job of creating a new storyline that still feels true to the original Harry Potter universe. There are some really emotional moments between the two characters.