To transform the given sentences into a more expressive form using comparatives and superlatives, let's analyze each one and apply the necessary changes.
Never have I seen such a fantastic show!
- It's the most fantastic show I've ever seen.
I've never read such a bad poem.
- It's the worst poem I've ever read.
I've never seen such a funny film.
- It's the funniest film I've ever seen.
To our great surprise we found one immediately.
- The surprise was all the greater because we found one immediately.
I have never met such a silly woman.
- She is the silliest woman I have ever met.
As he advanced, the jungle became thicker.
- The further he advanced, the thicker the jungle became.
I have never seen such fat people as the Americans.
- The Americans are the fattest people I have ever seen.
Danger increases if you drive fast.
- The faster you drive, the more the danger increases.
I have never heard a more stupid story.
- It is the most stupid story I have ever heard.
Mary's coat is more expensive than Kate's.
- Kate's coat is less expensive than Mary's.
I have never heard such a dreadful singer!
- He is the most dreadful singer I have ever heard.
There are more students in my school than in yours.
- There are not as many students in your school as there are in mine.
I've never read such a good thriller in my life!
- It's the best thriller I've ever read in my life.
He's never played such a good game.
- This is the best game he has ever played.
I have never heard such a talented pianist.
- This man is the most talented pianist I have ever heard.
When you don't sleep much, you feel tired.
- The less you sleep, the more tired you feel.
Sting is the most dedicated singer in the music business.
- There isn't a more dedicated singer in the music business than Sting.
I've never eaten anything as bad as that.
- This is the worst thing I've ever eaten.
I've never seen such a good film!
- This is the best film I've ever seen.
For sentence 20, the text seems to be cut off, so it cannot be completed without further information.