What is the worlds worst worst pandemic ever?

The Black Death in the 14th century and the Spanish Flu just after WW 1 are a couple of examples of terrifying pandemics that left many dead in their wake. They were far worse than COVID-19. How long will the current pandemic last? Your guess is as good as mine.

The Black Death during the middle ages killed on third of the population of Europe.

The Black Death was the worst, because they lacked any kind of decent medicine.
Covid 19 on the other hand is being well managed, we have treatments and hope of a vaccine very soon, and everyone is bewing well communicated with.