According to what appears to be the source of the chart of the OP meme, the absolute highest rate of myopericarditis is specifically among 16-17 year old males after getting the 2nd dose of the Pfizer vaccine........Based on the number of reports, the rate of myopericarditis for that very specific group is 0.00715%....And that is the highest specific group by far.
The next highest group is 12-15 yr old males, Pfizer, 2nd dose @ a rate of 0.00426% .. And it looks like the rate declines broadly across all groups younger or older than 16-17.
In any case it looks like myopericarditis is by no means a death sentence. Information from VAERS case reports suggests most (77%) of the patients who were affected by myopericarditis have recovered from symptoms at the time of the report or follow-up.
This is all based on what appears to be the OP source (a PDF file):
"Myopericarditis following COVID-19
vaccination: Updates from the Vaccine
Adverse Event Reporting System (VAERS)"
Aug 30, 2021
John R. Su, MD, PhD, MPH