The original Amnesty International report didn’t have any figure for China, it simply said that in China there were more executions than in other countries combined. China has also more people than other mentioned countries combined. A quick wiki search gave me these numbers – executions per 1mln:
China (assuming 1000 executions): 0,75
Iran – 5,23
Iraq – 3,84
Saudi Arabia – 2,41
USA – 0,17
Yemen – 1,27
Sudan – 0,21
Vietnam – 0,10
Syria – 0,36
Japan – 0,05

With all my reservations about China, actually these numbers doesn’t look so bad for them. They are simply big, populous country.

I’m intrigued by your question. Deciding to portray this kind of data as a ratio (killings per million or killings per total population) papers-over the Chinese and American records and invites comparisons to “worse” records instead of better ones. For example, it does not invite comparison to India, France, Germany, and other populous countries that did not make this top-10 list. As always, it comes down to the overall purpose of the chart.

So I kinda’ like the use of actual numbers of killed prisoners. Each one was a human, not a ratio.

I’m relieved it was not portrayed with photos and I’m rolling my eyes at colouring China’s bar red. Still scared are we?

USA and Japan are the only develop countries according to this chart.