You mentioned in a reply above that you're currently out of budget, which makes a "total rework" kind of fix out of scope.
What about some "distraction" type of fix? Get a printed peel-and-stick wallpaper with an irregular pattern that distracts from the asymmetry and will be fine for now (for real, or ironically) until in a few years you can't stand it any more but have the $ for a more substantial fix.
Edit: You could apply this to the part above the tile, but also you could apply this to the tile. Whatever "distracts" more and works well with the pattern you choose...
Either re-tile, or re-paint, with some sort of irregular pattern that makes it almost impossible to see the uneven lines.
This will require giving the bathroom "character", and many buyers are not great fans of "character", but it is the most expedient way to mask the error.
And it's hardly new in architecture; things like popcorn ceilings or knockdown drywall are designed to hide flaws in drywalling.