"It's really good to see you!"
This one happens all of the time. You maybe run into an old "friend" at the grocery store from high school who you haven't talked to in years, for good reason. Or maybe you run into that person that your friend set you up with or that Tinder date you only went on one date with because, well, the date sucked. But, if you see them out in public, you pretty much have to make with the nice greeting, because being as honest as you'd probably like is a bad idea.