whats going in the empty space?

Dishwasher. That's the dilemma. I could shrink the left cabinet to a 9", and change the right cabinet to a 33", but that would mean trying to return cabinets that have already been installed. Also, 9" cabinets are not very useful, and this is a very small kitchen, so the 12" adds more storage space.

Symmetry is overrated.

Symmetry IS over rated. BUT. This would be crazy making to have something so non symmetrical. It's unbalanced. Assemetry relies on balance to achieve harmony. This is just poorly designed, not asymmetrical.

But, it's a rental, and will be destroyed in no time, so fix it the next time you replace cabinets on a couple of years time.

I agree that it will look awkward. If the sink is in front of a window that size, it really needs to be centered for the right look and the cabinets should be designed around that. As far as the comment about a rental being destroyed in a couple of years, I have seen many rental properties that are very well taken care of. The secret to that is to be a very conscientious property manager, being very choosy about the people you rent it out to, and then checking in frequently to ensure that they are taking care of it. Be sure your rental agreement contains legal language for liability so your renters know exactly what you expect. Good Luck!

For a rental no one is going to care. No one would decide not to rent a place just because the sink is off center. If it was your own kitchen renovation I would re do it.

To ease the asymmetry of the cabinet I would center a pendant above and center the sink faucet placement with the window. Cabinets look great otherwise!