How do you deal with a peer who wants to write a bad code just because he doesn't understand the better way to write it or he just doesn't want to?

Suppose you're not in a company, so there's none above you two, like you're freelancers or in a uni team for a project

If you're their manager, you talk with them about coding standards, explain to them why this way is meaningfully better, and you make sure it's addressed before the code is merged.

If not, you make the suggestion but if they ignore it, bleh. Not worth worrying about.

*please don't let that be me*

@AlmondSauce what if you're the manager, go through it multiple times and it still gets ignored? and you're in ops not dev, so the tooling/scripting comes as "voluntary extra", meaning you can not fire that person as poor code quality does not impact the core work

@qwwerty Firing seems extreme, but you certainly make a note of it and bring it up in performance review, then perhaps withold a raise or promotion until that sort of thing is dealt with. Doesn't matter if it's a core responsibility or not, if it's something the employee is doing then they should be doing it right.