Oddly enough, his opposite house is Ravenclaw.
While Scorp is far from your typical Hufflepuff, he is very loyal to the select few he thinks deserve it, and is extraordinarily hard-working if he thinks that the effort will be worth it. However, he can be quite lazy if he isn't passionate enough about something, and is terrible when it comes to teamwork.
Scorpius spent much of his Hogwarts years hating everyone who wore red and gold, and is still in denial that one of the reasons for this was jealousy. Scorpius is brash, sociable, often takes risks, and can be brave. If he had been born to another family, it is possible that he would have ended up here. Now, however, he is so far from a Gryffindor that he finds others openly expressing emotions both confusing and embarrassing.
While many consider Slytherin and Ravenclaw to be the most similar houses, Scorpius is a perfect example of this not always being true. Scorpius is smart, but completely lacks work ethic. He is lazy, often careless, and generally of the opinion that learning is simply the means to an end. He also completely lacks organization, and would've been completely at a complete loss with what to do with a common room full of Ravenclaws.