I came across Kristina Tremonti through this article in Der Spiegel (the article is in German but the video at the beginning is in English). Here is another video about her fight against Greek corruption. And here is an English article from The Guardian.

Tremonti was born in Vail, Colorada, as daughter of an Italian father and a Greek mother. At age 2, she moved to Greece with her mother and at age 16 she returned to the US for studies, and she later received a degree from Yale University. At age 23, she left a well-paid job in NYC to return to Greece to make a contribution to her mother's home country. She is now 27.

After having had to pay a bribe ("fakelaki") to get her grandfather a cancer operation in a Greek hospital, Tremonti chose corruption as the field of her activity. She established the platfrom www.edosafakelaki.orghttp://www.edosafakelaki.org/.

I have browsed her activities in the internet a bit and everything sounds really quite impressive!