What is the hardest cloud certification?

I'm curious to know, out of all the various cloud certifications available, which one is considered the most challenging to achieve? It's a common sentiment among professionals to strive for the most prestigious and demanding certifications in their field, so I'm eager to learn which cloud certification holds that title. Whether it's due to its rigorous exam requirements, extensive knowledge prerequisites, or the sheer complexity of the material covered, I'm interested in hearing your take on what sets this particular cloud certification apart as the toughest to obtain.