When it comes to sorting students into the different houses in Hogwarts School of Witchcraft and Wizardry, it's kind of two sides of the same coin in a strange way. Each house has particular characteristics that they value over everything else, but a student can be chosen for that house because they already fulfill those characteristics or they can be chosen because their personality is in direct opposition to those traits and they need an education in that particular house to bring those traits out in them.
And when it comes to Slytherin house, one of their most prized personality traits is ambition. Salazar Slytherin wanted to teach students who wanted to excel, and who saw themselves as the type of wizards that could go down in history as one of the best. But because students are often placed in houses that contradict their personalities at the beginning of their Hogwarts education, Slytherin has wound up with plenty of lazy students too. So here are the 5 most ambitious Slytherins, and the 5 laziest.
10 Ambitious: Dolores Umbridge
When it comes to the ambition of Slytherin, no one character in Harry Potter more adequately represents the darkest side of that ambition than Dolores Umbridge. Umbridge is not a particularly talented or clever witch on any level, but her ambition, sneakiness, and willingness to do things that any normal person with a conscience wouldn't dare think of is how she has gotten so far in her life.
She tends to overrate and embellish upon everything that she or her family has done, and she will do things that repulse her if she thinks it will get her further in life (even if that includes dealing with children).
9 Lazy: Gregory Goyle
Gregory Goyle is so lazy that he doesn't even have a personality, he was always just waiting for someone that he could follow that would actually give him one. As one of Draco Malfoy's favorite thugs, Goyle seemed to take a good amount of pleasure in mistreating and bullying children, but nothing else in life seemed to provide him with much pleasure or excitement.
Alongside his partner in crime Vincent Crabbe, he terrorized every child he could get his hands on that was younger or smaller than he was (which was pretty much all of them), and he was more than content to ride Draco's coattails for his entire Hogwarts career.
8 Ambitious: Merlin
The world of wizards and witches and the world of muggles seem to have been separated since wizards and muggles discovered that they were actually different from one another, but one particular Slytherin student aimed to change that. Merlin is a literal legend of magic, and he's one of the few magicians that the muggle world is aware of. And that's for a reason.
Merlin believed very strongly that muggles and wizards needed to learn to live together and cooperate, and he apparently had no problem being the guinea pig for that experiment. Wizards and their views on muggles tend to vary, but even the pro-muggle wizards haven't single-handedly tried to blend their world into ours like Merlin did.
7 Lazy: Vincent Crabbe
Vincent Crabbe is Draco Malfoy's other lackey, but he may as well be called bully #2. He doesn't bring anything else to the table besides his willingness to torment other students for no apparent reason, and he is another boy who clearly wants to be a follower.
That's not even because he wants to be cool either, it's just because he's too lazy to even think on his own. And really think about Crabbe and Goyle as a team. They're bullies in magic school who physically bully children instead of using magic to do it. They're too lazy to even learn something that will up their game as tormentors.
6 Ambitious: Salazar Slytherin
Obviously he didn't come up with the idea on his own, but along with the rest of the founders of Hogwarts School of Witchcraft and Wizardry it's clear that Salazar Slytherin had to be extremely ambitious to decide to create what would become one of the best wizarding schools in the world.
And on top of his ambition to create the school, he also quite literally wanted to make his house into the house for ambitious students. He wanted to fuel their own ambitions and create an environment in which they could flourish and maximize the potential that their natural drive gave them.
5 Lazy: Draco Malfoy
From the very moment that the readers and watchers of Harry Potter met Draco Malfoy, his intent and beliefs were obvious. Draco is one of the laziest Slytherins of all time simply because he doesn't believe that he should have to work for anything, ever.
He believed in his own inherent superiority because he was a pure-blood wizard from very powerful and old bloodlines, and he never concerned himself with working because he believed that everything he needed could be bought. And sadly, for the most part, it seems like he was right, he managed to coast through school without putting any work in simply because he was a Malfoy.
4 Ambitious: Severus Snape
Clearly grief and blind fury are what drove Severus Snape to make the choices he made after Lily Potter was killed, but you really have to tip your hat to the fact that Snape, a talented but still not wildly exceptional wizard, decided that he would be the one to single-handedly take down the darkest, most powerful wizard who ever lived.
Most wizards didn't even have the gumption to stand up against Lord Voldemort, but Snape seemed confident that he would be the one to exact revenge on Voldemort, or die trying. And he did die trying, but at least his goal was achieved in the end anyway.
3 Lazy: Lucius Malfoy
As a child, Draco Malfoy was the slimiest, most arrogant little jerk you'd ever meet, but it's not hard to see where he got it from. Lucius Malfoy was an illogically cruel and haughty individual, especially since his lone "achievement" in life was being born into the Malfoy family.
He was willing to actually act in circumstances where he stood to gain something, but he was generally an extremely weak and cowardly man who solely valued money, his own money as well as the money of others. Lucius didn't work but expected everyone around him to, and he still thought he deserved more respect than everyone simply because of who he was.
2 Ambitious: Tom Riddle
Obviously ambition as a quality can be a really wonderful thing or a really terrible one, and when it comes to Tom Riddle clearly his ambitious nature went about as dark as ambition can go.
Even very powerful wizards rarely look at the world and see it as something that they can conquer and claim for their own, but as a child Tom seemed to see the world as his for the taking. He was a terrible man, but he achieved things unlike anything the world had ever seen, and it took an enormous amount of ambition and force of will to make that happen.
1 Lazy: Horace Slughorn
Horace Slughorn is actually a fascinating example of a Slytherin, because he did have a lot of ambition but he was also an astonishingly lazy person. He was so lazy in fact, that he essentially tried to collect people that he thought would achieve great things and steal some of their glory just by being associated with them.
He certainly values achievement more than anything, and he completely disregards students who he doesn't see potential in, but he has never achieved anything worthwhile himself. He probably could prove himself as a powerful wizard if he wanted to, but he's just too lazy to do any work himself.