"Ugly" in physical terms is subjective.
It isn't. As a pp said, there are degrees of subjectivity but broadly speaking there are physical characteristics that humans find attractive and physical characteristics that humans find repellent.
If I searched for random pictures on the internet and posted 9 of attractive women and one of an ugly woman, it would be very obvious which one was the ugly woman.
Yes, there are 'tactful' cliches such as the Dahl shite and 'you have a lovely smile' or 'you have a kind face' but none of that changes anything if you fall in the ugly camp.
However things do get better when you hit middle age because you become invisible, and you see the faces of your attractive contemporaries start to sag, wrinkle and droop, so things level down a bit.