The Wizarding World is home to many complicated antagonists. For example, while there are purely evil villains like Voldemort and Bellatrix Lestrange, others have a more complex outlook. A great example is Severus Snape and how even when he acts on the side of Voldemort, he's actually devoted to protecting Harry Potter. However, one unexpected character that is wildly complex is Lucius Malfoy, and even though he nurtures that complexity throughout multiple films, one act nearly made him as evil as Voldemort.
When he's first introduced in Harry Potter and the Chamber of Secrets, Draco Malfoy's father is an aristocratic wizard who prides himself on his pure-blood lineage. However, he's also manipulative and mildly abusive toward his son, who wants nothing more than his father's approval. Lucius was also on Voldemort's side during the First Wizarding War as a Death Eater, but his cowardice and survivability would shine through as he avoided jail time by saying he was controlled by the Imperius Curse the whole time. While living his life and caring for Draco, he also had a House Elf named Dobby that he treated poorly every day.
Dobby would later save Harry on multiple occasions, and, upon seeing how he was treated, even gave him his sock to free Dobby from the Malfoy's service. While most enraged adults would likely scold a child for being inconvenienced, Malfoy's dark side was briefly teased as he took out his wand and directed it at Harry. As he approached, he began to utter the beginnings of the Killing Curse, but Dobby stopped him. Ever since, Harry never realized how close he came to dying or how Dobby may have sent Lucius on a long path of redemption.
From that point on, Lucius would return to the service of Voldemort, but his favor would gradually dwindle into nothing. Following the destruction of Voldemort's diary and Malfoy's loss at the Department of Mysteries, Lucius appeared as anything but competent in the Dark Lord's eyes. As a result, he manipulated his emotions by taking over the Malfoy mansion and threatening to kill his family while belittling Lucius. In the end, the man of wealth and status was left with neither.
Ultimately, his need to survive and protect his family would lead Lucius to betray Voldemort. With the Dark Lord defeated, he and his wife Narcissa turned in every Death Eater they could to avoid being imprisoned in Azkaban. That being said, their respect would never be the same, and Draco's choices as an adult would also serve to spite his father. Perhaps the most monumental would be with the birth of his son Scorpius. Rather than teach him the same lessons of pure-blood superiority that he learned, Malfoy and his wife taught their son to accept every wizard, much to the chagrin of Lucius.
Lucius is by no means a good person, but by Dobby saving him, he was given a chance to live a life that wasn't filled with death and destruction. Ironically, the moment came when Malfoy himself nearly killed a child out of anger. Although the scene is brief, Malfoy's decision shows just how close Harry has been to dying without even realizing it. However, Dobby's intervention gives even someone as undeserving as Lucius Malfoy a path to redemption that he would eventually take, even if he never fully recovered from its effects.