Trimming or spackling the edge of a tile schluter to drywall (Large Gap)
Sometimes aesthetics are more important than "level, square, and plumb".

Try scraping that stuff back a bit and doing it over with lightweight topping compound. Use a smooth clean knife and the stuff goes on like butter, and it's easy to sand smooth after it sets. Hit it with primer and paint and it will look as good as it is going to.