Corruption is both a major cause and a result of poverty around the world. It occurs at all levels of society, from local and national governments, civil society, judiciary functions, large and small businesses, military and other services and so on. Corruption affects the poorest the most, whether in rich or poor nations.
The issue of corruption is very much inter-related with other issues. At a global level, the "international" (Washington Consensus-influenced) economic system that has shaped the current form of globalization in the past decades requires further scrutiny for it has also created conditions whereby corruption can flourish and exacerbate the conditions of people around the world who already have little say about their own destiny.
A difficult thing to measure or compare, however, is the impact of corruption on poverty versus the effects of inequalities that are structured into law, such as unequal trade agreements, structural adjustment policies, so-called "free" trade agreements and so on. It is easier to see corruption. It is harder to see these other more formal, even legal forms of "corruption."
It is easy to assume that these are not even issues because they are part of the laws and institutions that govern national and international communities and many of us will be accustomed to it--it is how it works, so to speak. Those deeper aspects are discussed in other parts of this web site's section on trade, economy, & related issues. That is not to belittle the issue of corruption, however, for its impacts are enormous too.