I'm not sure about "a single person" but I believe Flask and Requests (both Python libraries) are/were at least strongly connected to a single 'creator' (Armin

I'm not sure about "a single person" but I believe Flask and Requests (both Python libraries) are/were at least strongly connected to a single 'creator' (Armin Ronacher and Kenneth Reitz respectively) that come to mind for me, though both have larger communities of contributors these days.