As one of the most recognizable villains in Harry Potter, Voldemort has to have a pretty scary looking face. But, it wasn't always that way. In fact, Voldemort used to look a lot more like Tom Riddle, and he only lost his nose when he started experimenting with Dark Magic. It was never explained why Voldemort's nose became flat and slit-nosed, but it is a key part of his appearance that ties in with his connection to snakes.
It is important to remember that Voldemort grew up as a normal human child. He went to Hogwarts, was a handsome student and had a normal nose until he began to experiment with Dark Magic. His descent into evil was rapid and drastic, and as a result he began to lose all traces of his humanity. His face and body became pale, he got rid of all of his hair and he even disfigured himself to resemble a snake.
As a result, he started to look more and more like the snake that he had been born as and that's how he ended up looking in the movies. The movie Voldemort is a terrifying serpent figure with deathly pale skin, rough rakes, and cat-like eyes. It is a perfect representation of his cruel and cold personality. He also had a special connection with snakes and spoke Parseltongue, the language of snakes, and kept a large snake named Nagini as his pet.