Eleanor's stepdad, Richie, is beyond evil—he's in straight-up monster territory—and his presence is so terrifying that it's felt in Eleanor's house even when he's not home, creating an atmosphere of constant fear.
Eleanor's family lives in terror of setting off Richie's temper, and it doesn't take a lot to trigger an eruption. Eleanor describes the state of terror as "crazy. Diary-of-Anne-Frank crazy" (6.32), and sadly, she's not exaggerating. Richie's temper is so bad that he threw Eleanor out of the house after an intense shouting match because her typewriter was too loud. Seriously.
We're not even sure what Richie does for a living, and as far as we can tell, he's primarily an alcoholic—and when he drinks (which is always), he gets violent. He spends every single night at a local watering hole called the Broken Rail. Eleanor thinks he looks "Like the human being version of a rat" (10.10), and she gives Park a chilling description of her stepdad: "He's the kind of bad that tries to kill anything good" (19.330). That pretty much says it all.
We don't know a lot about Richie's background, other than the fact that he's lived in Eleanor's neighborhood forever. Park's dad grew up with him, and in the understatement of the year, tells Eleanor, "I know your stepdad isn't an easy man to be around" (35.14). Park's dad also tells Eleanor to come stay with them whenever she wants:
"I'm just saying, you know, that if it's easier to be over here, then you should just be here. That would make Mindy and me feel a lot better, okay?" (35.14)
Park's dad's offer tells us a whole lot about Richie, if you read between the lines: He doesn't trust Richie, and more than that, he could imagine Richie doing something bad if left alone with kids. His instincts are spot on.
Before Richie chased Eleanor out of the house for a year, all the kids were allied against him: "Eleanor hated him the most, and the most openly—but they were all on her side, Ben and Maisie, even Mouse" (6.47). The siblings talked about how much they hated him:
"I hope he falls off a ladder at work."
"I hope he gets hit by a truck."
"A garbage truck."
"Yeah," Maisie would say, gritting her teeth, "and all the garbage will fall on his dead body." (6.52-55)
But when Eleanor returns from her year away, she finds her siblings have switched alliances in an almost creepy way. They're all calling Richie Dad now, and Eleanor implies that maybe he's molested Maisie, Eleanor's younger sister. Given how afraid Eleanor is to bathe with Richie in the house, we're not so sure he hasn't tried to lay hands on her, too—especially considering the sexual notes he leaves on her schoolbooks throughout the year.
After Eleanor's return, her family's clearly given up the fight against Richie. They listen to him assault Eleanor's mom every night, and grow so accustomed to it that they don't even wake up. If you wonder why they don't call 911, it's because it seems pointless:
[…] it seemed like something a child would do, or a fool. Now, all [Eleanor] could think about was what they were going to do if the baby actually started to cry. Thank God he didn't. Even he seemed to realize that trying to make this stop would only ever make it worse. (11.19)
Richie's family may still technically be alive, but he's done his darndest to kill their spirits.