"more unprecedented" is a correct phrase in written English.
You can use it to describe something that is even more extraordinary than expected. For example, "The coronavirus pandemic has led to more unprecedented changes in education than ever before."
This election may well be unprecedented but there are many more unprecedented events yet to come.
What makes this even more unprecedented, though, is the company's legal promise not to spy on CAAT in the future.
We hope that in hindsight we will find out that we were wrong, and global warming is not leading to more unprecedented extremes.
That all sounds like a dramatic volte-face, but it turns out to be even more unprecedented than it first appears.
That decision was all the more unprecedented since the lone witness changed his mind twice about the year in which the alleged offence occurred before deciding that he could not provide any specific date at all.
The eurozone faces worryingly low inflation – and even outright deflation in some member states – and with growth flagging the ECB is contemplating yet more unprecedented measures to turn things around.
But Mr. Wang, these people said, also apparently revealed far more: an unprecedented trove of knowledge on the leadership struggle.
Once again, North Korea is threatening to reduce South Korea "to ashes" – what's more, "by unprecedented peculiar means and methods of our own style". A tense and nervous world is wondering what to do.
Federer has won 10 tennis titles or more an unprecedented three straight years.
I see it in the call for more and unprecedented public/private partnerships.
Hydrograph peak discharge estimation is gaining more significance with unprecedented urbanization developments.
