Negative with comparatives ( it got me confused)

[M!do]

Hello,

How are you? Hope you're doing well.


I'm really confused with these sentences,


It could have been more difficult.
It couldn't have been more difficult.
It could have been worse.

He couldn't have been more unfriendly.
He could have been more unfriendly.


I will be grateful to whom clarify them to me.

[Raymott]

Hello,

How are you? Hope you're doing well.


I'm really confused with these sentences,


It could have been more difficult. "It wasn't that hard at all. It could have been much more difficult."
It couldn't have been more difficult. "It was very difficult - so difficult in fact that it could not have been any more difficult than it was."
It could have been worse. "Ok, you broke you toe. It could have been worse. You could have broken you whole leg."

He couldn't have been more unfriendly. as above
He could have been more unfriendly.

I will be grateful to whom clarify them to me.

You can try to explain the last pair.

[M!do]

You can try to explain the last pair.

Oh, thank you so much for explaning.

Ok, I'll try, but, please, tell me if I did it well.

He couldn't have been more unfriendly. ( He was unbearable, he was extremely rude)
He could have been more unfriendly. ( He was, as usual, unfriendly)

What about these two sentences?

He couldn't be happier ( He was extremely happy)
He couldn't care less ( He didn't care at all)
He couldn't care more. ( He was extremely interested)

Did I explain correctly??

[emsr2d2]

Oh, thank you so much for explaning.

Ok, I'll try, but, please, tell me if I did it well.

He couldn't have been more unfriendly. ( He was unbearable, he was extremely rude) However, note that in order to be unfriendly, it's not obligatory to be unbearable or extremely rude. It's just the opposite of "friendly".
He could have been more unfriendly. ( He was, as usual, unfriendly) There is no way to tell how he usually behaves. The statement simply means that he was unfriendly but probably not as unfriendly as it's possible to be.

What about these two sentences?

He couldn't be happier ( He was extremely happy)
He couldn't care less ( He didn't care at all)
He couldn't care more. ( He was extremely interested)

Did I explain correctly??

See above.

[M!do]

Ah, I got it.

Thanks a bunch.