The game ends as soon as you get 10 or more points, so even if you can build multiple things, the one that gets you to 10 is it.
I'm fairly certain that the highest score possible in Catan is 12 points. Assuming you are at 9 points, and are in second place for longest road, if you were able to build a settlement that broke up longest road that would give you three points at once.
Is there a way to end with a higher score?