always; when you tell sb to do sth without fail, you are telling them that they must do it
Oxford75% of films
always
Rapunzel, how you manage to do that every single day without fail.
Oxford25% of films
when you tell sb to do sth without fail, you are telling them that they must do it
I'll have her here tomorrow morning at ten without fail.
Definitions from the Oxford Advanced Learner's Dictionary, 9th edition