How much inflation is too much inflation?

From the BBC World Service: The European Central Bank seems to be taking a page out of the U.S. Federal Reserve's book, incorporating some flexibility on inflation, as economies react to the easing of COVID restrictions. Plus, the assassination of Haiti's President Jovenel Moïse is a fresh blow to the Caribbean country, which has a long history of political instability and dismal economic performance. And, as COVID cases rise, Japan declares another state of emergency in Tokyo for the duration of the Olympic Games this summer.