He was deliberately being hurtful and spiteful. Della didn't just come back and say "sorry," she spent 10 years agonizing over her mistake, trying to get home, and when she finally got back she threw herself into their lives trying to make up for her failure to be there. Not saying she didn't fuck up along the way, but she was absolutely doing her best to make up for her mistake.
Louie fucked up a get rich scheme... again. He keeps doing it. "Sorry" with no punishment enough wasn't going to cut it.
Not saying that the writers did wrong there. He's a kid, kids can be spiteful and petty even when caught with their hands in the cookie jar.
But Della was in the right to be going "no, sorry isn't going to cut it," and his response was him being a little shit that didn't like having real consequences for his fuckups.