Reject their patches.

Literally "this is a small, simple feature. It should take something like 200 (or 10, or 50) lines to implement. 3000 tells me you didn't think carefully enough"

Or "you have a bug here, a bug here, another here. This is where I stopped. Ask me back when it's ready for review"

I promise you that their code is not all great. It takes an order of magnitude more effort to refute bullshit than produce it. Refute part, then don't engage with the rest. They'll get the message.