Incredibly
Part of speech: adverb
Definition: In an incredible manner; not to be believed. To a great extent; extremely. .
Example sentence: Grief is never something you get over. You don't wake up one morning and say, 'I've conquered that; now I'm moving on.' It's something that walks beside you every day. And if you can learn how to manage it and honour the person that you miss, you can take something that is incredibly sad and have some form of positivity.
Unbelievably
Part of speech: adverb
Definition: In a manner that one does not believe.To an extent not to be believed.Contrary to expectations, amazingly.
Example sentence: Humans are unbelievably data efficient. You don't have to drive 1 million miles to drive a car, but the way we teach a self-driving car is have it drive a million miles.