I agree that ending an interview early is a no-go. However if it's an onsite/process with multiple interviews, I think the fairest approach (and I've done this in the past) is to manage expectations ahead of time that the full interview sequence only happens if you pass each one.

This way you don't waste the candidate or your time if it's clearly a no after interview 1. They feel a bit bad because they obviously didn't pass, but if you've communicated ahead of time it's not a rug-pull.