Honestly this is a simpler answer than what people think. Just go to per capita stats and do a mixture of deaths/capita and cases/capita
Here is my very rough methodology. Take the world average of cases/Capita and deaths/capita. Then see what percentage above or below the world average each country is (for example if the world average is 100 deaths and a country has 200 deaths, that means it gets 200%). Then average the 2 numbers for the deaths and cases above the world average.
Doing this very rough methodology you get the following list of the top 20 worst responses (I'll exclude microstates and places which are not really countries or are unrecognized and put them in italics):
Andorra
Faroe Islands
San Marino
Monaco
1 Luxembourg
Gibraltar
2 Peru
3 USA
4 Spain
5 United Arab Emirates
6 Bahrain
Channel Islands
7 Italy
8 Chile
9 Iceland
10 Brazil
Falkland Islands
11 UK
12 Sweden
13 France
Cayman Islands
14 Panama
15 Ireland
16 Mexico
Sint Maarten
17 Bolivia
18 Colombia
19 Netherlands
20 Ecuador
On that note, here would be the top 20 best responses to COVID, which is an slightly more surprising set of countries:
3 way tie at 0: Vatican City, Seychelles, Eritrea
1 Tanzania
2 Timor-Leste
Western Sahara
3 Burundi
4 Papua New Guinea
5 Dominica
6 Burkina Faso
7 Democratic Republic of Congo
8 Myanmar
9 Angola
10 Niger
Taiwan
11Mozambique
12 Ivory Coast
13 Chad
14 South Sudan
Anguilla
15 Laos
16 Somalia
17 Cambodia
Macao
18 Guinea
19 Syria
20 Tajikistan
You could add testing to the mixture as well I guess if you want to account for that, but I have not done that for now.
Anyways my comments:
1: Tfw Syria and Somalia are doing better on covid than your own country 
2: As expected, underdeveloped 3rd world countries seem to be the ones doing better, despite the initial fears of covid wrecking Africa that has not happened (if anything, the opposite is true)
3: Much more surprisingly, both the Chinese "special zone" of Macao; as well as the de facto independent country of Taiwan are doing quite well; and these are not dirt poor places of the world but rather more "middle income" ones. I wonder why they did so well; maybe Jachind can explain it somehow?
It seems likely that measuring by cases is misleading because if you don't/can't test then you'll only find the most deadly cases. Also, not all cases are equal: considering the drastic difference in deaths between New Jersey or New York and Texas, California or Florida despite comparable case loads.
The best way to measure success would be to average the death rate with the relative change in GDP growth.
