The ever lovin’ blue-eyed thing is a Hufflepuff mainstay. Strong, decent, and loyal, its easy to imagine the Thing in the classic yellow and black. The thing is (pun definitely intended!), I feel that in his human form, Ben Grimm would have probably been a Gryffindor, but his transformation to The Thing slowed him down and allowed his true qualities to emerge, making him an honest and open-minded man.
A bit of a cheat, but you can’t have one without the other. Fire and Ice are Hufflepuff mainstays who personify the house’s belief in patience and hard work through their friendship alone. The two have stuck by one another through thick and thin, from bad boyfriends to resurrections. Both women also were part of the original UN Global Guardians Team and members of Justice League International, teams that were meant to encourage unity between the Earth’s nations. It didn’t take, but it was worth a shot.
I know that the first two Flashes were scientists, but Hufflepuffs are allowed to have outside interests. The reason why the entire Flash family is in Huffepuff is because most Flashes tend to really get along with everyone. Jay Garrick founded the Justice Society and acted as a role model for an entire generation of heroes. Barry Allen could talk shop with Batman, keep up with Superman, and joke with the Green Lantern. Wally West could do the same, as well as hang out with people like Nighwing and Donna Troy.
I was really tempted to put Captain America in Gryffindor, but as I read what the Hufflepuff house looked for in a member, I had no other choice. Yes, Captain America is probably the bravest Avenger, but Cedric Diggory was brave too, and we should all remember that most Hufflepuffs fought in the Battle for Hogwarts. But being dedicated, hard working, humble, and honest is kinda what Captain America is all about.
Supergirl belongs with Hufflepuff because she doesn’t really fit anywhere else (a common problem with her character). She’s brave, but their are braver. She’s smart, but no real genius. She’s not terribly ambitious, even naming herself after her more famous cousin. The thing is, Supergirl is a bit more normal than people realize, since she got her powers as a teenager instead of growing up with them like Superman. As such, she doesn’t really dive into the superhero game like Clark Kent, but she’s always there to help when needed. In the meantime, she’s just trying to live her life, like all true Hufflepuff.