What is the difference between extremely and witless?

For instance:
1/ We were extremely bored.
2. We were bored witless.

Thank you very much~

Question

What is the difference between extremely and witless?

For instance: 
1/ We were extremely bored.  
2. We were bored witless.

Thank you very much~

Answer

They are utterly different and can't be compared.
Extremely - adverb = very
Witless - adjective = without wits. (Wits are the ability to think clearly.)

We were very bored.
We were so bored that we were without wits.

Answer

Say #2 in informal conversation only. It is colloquial.

Answer

Bored witless is a fixed expression. I can’t really think of another use for witless.