Which country has the highest potential (permanent) investment return

I love the concept of generating a gigantic investment income as a way to play MD, so I was wondering which country has the highest potential for this strategy!

I have played the US, one which I know I can get 16%

I am currently playing the Netherlands, on which I currently have 14% permanent return

My question is basically what other countries have high potential investment returns (10% or higher) to play with this strategy, and also what country has the highest potential one? (if the investment returns are hidden in weird focus decision, please add what I need to do to unlock the investment return, for example for the netherlands its in a regular focus + the ing focus, and obviously the ruling party)