On Hope

Burnout comes not from working hard, or even working hard without reward — but from being worked hard without hope of improvement.
These conditions do not come about by accident — they are a product of company culture, planning, and management techniques.

So, if I were a manager with an employee I wanted to quit, here's what I would do:
Make the engineer responsible for a new project that is an executive's pet. Make sure that the stakeholders are notoriously demanding but difficult to get specifications out of. Bonus points if they've already vibed a mockup for the product frontend, and consider that to be most of the work done — even though it will actually be technically challenging and/or messy in ways that they don't get.

Make sure it's scheduled to go for at least two quarters, with the unspoken knowledge that it'll probably go for at least twice that, so they've got plenty of the same drawn-out horror to look forward to.

Apply continuous pressure that this project needs to be done now because there are competitors already doing it and eating our lunch, but don't allocate any time to work on it because you scheduled the project for several sprints' time, last quarterly planner.

Hype up the project in team meetings as 'high risk' and put pressure on the engineer by making a public deal of assigning them as the lead to make sure that they don't feel like they can escape the project's inevitable poor outcomes.

Don't assign any other engineers to the project - only provide the most under-your-skin tech-bro or technically deficient staff for the project management, BA, and frontend roles, so that the engineer won't want to hand off any of their work for fear of getting sub-par results.

Knock back requests for additional compensation or working environment changes by saying that it's not viable right now, knowing full well that they also know that if it "can't" happen right now, it won't ever — especially given the hazards of this project looming over their annual review process.

Those stakeholders? They won't want to spend time talking about requirements (it's all in their mockup, after all!), so there will be very few opportunities for the engineer to actually get concrete requirements out of the people who know how the system should work. Double down on this by occasionally coming around to their desk and verbally telling them something you picked up from the stakeholders that completely invalidates work the engineer has already done.

Et voilà — all it takes is to casually and consistently erode their hope for an improved future by taking away a little of it each week, and they'll burnout and be happy to be laid off to take up goose farming.