incapable of error or failure
infallible - unfailing
To be ‘infallible’ means to never be wrong, fail, or make a mistake. Since nobody is that perfect, this word is typically used with ‘not’ before it. However, it may sometimes be used in the context of something that always seems to be right or effective, even if that is not the case.
Don’t make your decision based purely on what others are telling you. Even the experts are not infallible.
Mike can always be relied upon to remember names and details. It’s like he’s got an infallible memory.
Our manager’s obstinate belief in her own infallibility means that she never takes advice from others.