Another word for without-fail

Some of De Morgan's most interesting and useful minor writings are to be found in the Companions to the British Almanack, to which he contributed without fail one article each year from 1831 up to 1857 inclusive.

A man came to the door, took my letter, and said madam should have it without fail.

The general orders them all to be driven out at once, without fail.

This requires you to plan and make sure that you have the resources to fully pay your bill each month without fail.

One product I've found after trying so many on the market that really combats creasing eye shadows without fail from MAC Cosmetics is called Paints, and the shade I prefer because it works on almost every skin-tone is, "Untitled."