The staff of Fortune and a panel of experts recently assembled our 2016 list of the World’s Greatest Leaders. Here’s a short profile of one of them.

He may be a funnyman, but John Oliver’s cerebral deep dives into social injustices on his HBO show Last Week Tonight have created a new form factor in comedy. There isn’t a topic he won’t tackle, from the plight of chicken farmers to native advertising to net neutrality. He insists he’s no more than a comedian, but his investi-comedy has effected change: his net neutrality piece was credited for a shift in the FCC’s position (and for crashing the agency’s website); last summer, a Ninth Circuit court judge cited his segment on U.S. territory rights in a class-action suit in Guam. (His Mother’s Day shredding of America’s parental leave policies, meanwhile, should be played on loop in Congress.)

The coup de grace may be his merciless pre-Super Tuesday takedown of Donald Trump: It’s been viewed about 23 million times on YouTube. As one of the beleaguered chicken farmers told Mashable, “If you’ve got a problem and you want it fixed, call John Oliver.”

This article is part of the World’s 50 Greatest Leaders feature, our annual list of world-changing leaders in business, government, philanthropy and beyond. Click here to see the entire package.