Draco and Harry are practically sworn enemies, originating from Draco's desire for Harry to befriend him instead of the Weasley offspring, a choice Harry did not make in Draco's favor.
Draco Malfoy and Harry Potter have always been fierce rivals at Hogwarts since their first year. Draco, arrogant and proud, hails from the Malfoy family, known for its pure-blood wizardry, wealth, and prestige.
Draco's father, Lucius Malfoy, is also a proud character who enjoys looking down on others, so it's no surprise that Draco Malfoy grew up with the belief that he is superior to others. However, Draco Malfoy can never compete with Harry in every aspect.
Is that the reason Draco Malfoy despises Harry Potter?
1. Draco Malfoy hates Harry Potter out of envy and a sense of rivalry

Draco Malfoy despises Harry Potter due to his envy of Harry's fame and magical abilities. Harry gained immense fame from birth, overshadowing others since his first year at Hogwarts, seemingly drawing all attention to himself. Part of the reason is being the only survivor of the brutal attack by the dark lord Voldemort.
Draco also looks down on Harry when he realizes the 'survivor' is just an ordinary kid, choosing to associate with the Weasley child and 'mudblood' instead of Draco, who comes from a more affluent background.
2. Their rivalry begins from their first year at school

3. Draco and Harry's children become friends

After getting married and having children, Draco also becomes a good father. He chooses not to raise his son the way his own father taught him.