The act of using one currency in the world mean's that every country in the world uses the same currency.
The use of a global currency will be the starting point of eliminating suffering in the world.
All nations would certainly benefit since there would no longer be currency risk in international trade. Traders would no longer fear for currency fluctuations.
Economically developing nations would also benefit base on the introduction of a stable currency, which would form a base for future economic development. For example, Zimbabwe suffered through one of the worst hyperinflation crises in history. The Zimbabwean dollar had to be replaced in April 2009 by foreign currencies, including the U.S. dollar.
It has gotten to a point in life where global currency is now needed in the world in other to end constant inflation and suffering in different countries.
When there is one generally accepted currency in the world, inflation and poverty will no longer be one country fight but a world fight.
Bitcoin is one digital currency I know that can do the job best prescribed by OP. However these concepts cannot happen. the reason is that, there is conflict of interest within Nations, there is religion intolerance within Nations and there are Nations that still want to dominate other nations.
So the concept of wanting to use one currency for everybody will have serious setback, and the currency formulation will it be controlled by world Bank or IMF, because if it is so a lot of people will see it as a political power play, because to some countries IMF and the world Bank are their enemy.
As for Zimbabwe and the hyper inflation they are facing, it's basically due to corruption and lack of productivity on the side of the government, even when Mugabe was alive as their president, the corruption level they faced was on a higher scale.