1.
If you describe something as ~, you are emphasizing that it is extremely painful, either physically or emotionally.
I was in ~ pain and one leg wouldn’t move...
= unbearable
ADJ emphasis
~ly
He found the transition to boarding school ~ly painful...
ADV: usu ADV adj, also ADV after v
2.
If you describe something as ~, you mean that it is very unpleasant to experience, for example because it is very boring or embarrassing.
Meanwhile, the boredom is ~...
There was a moment of ~ silence.
ADJ
~ly
The dialogue is ~ly embarrassing.
ADV: usu ADV adj, also ADV with v