This website tracks 215 countries, plus a few cruise ships, where Corana Virus is reported.
The top 13 yesterday (31 May) were:

I've added a column on the right showing Total Deaths as a percentage of Total Cases. It compares the number of deaths with a Certificate identifying Covid-19 as cause with the number positively tested for Covid-19, ie Total Cases. Both numbers imply medical supervision, probably hospitals. I don't think the figure has any relationship to population density or other external factors, it indicates the effectiveness of the Health Care system.
Worst performer is France(15.25%), then Italy(14.34%), and the UK(14.01%)
Comparable countries include: Spain(9.47%), Canada(8.02%), USA (5.78%), and Germany (4.69%) On the face of it a positive Covid-19 test is about 3 times more likely to be fatal to a Brit than a German.
Why?
Too early to tell, years of analysis and argument ahead! I suspect the root cause in the UK was shortages, particularly ventilators and the staff needed to run them. Just a guess because history suggests the UK is good at theory but very disinclined to spend money preparing for emergencies that might never happen. After all we are caught with our pants down every time it snows!
Another comment, only a small number of countries have so far reported more than 100,000 cases. There are plenty of countries nowhere near this number, therefore their statistics are unreliable. For example Australia has only had 7195 positive tests, which sounds like good news and maybe is. But we don't know yet if countries like Australia have successfully weathered the storm, or if the virus will run amok there in due course. Brazil, Mexico and Chile all reported similarly low numbers until recently, now they're showing Corona Virus is spreading rapidly.
It's not over until the fat lady sings!
Dave