Mangrove Partners is one of the best performing hedge funds in recent years. It was founded by Nathaniel August in 2010 with only $12 million in AUM. It returned 44% annually in its first 3 years. It isn't uncommon for small funds delivering big numbers in their first couple of years (if they are successful, they will use these return numbers to attract large amounts of capital).
Mangrove Partners continued to deliver large returns though. It returned 26.6% in 2014 and an average annual return of 20.6% for 2012-2014. We couldn't find its 2015 but it can't be good. However, Mangrove Partners made up for that by returning 50.9% after fees in 2016.
Nathaniel August is an activist and special situations investors who previously worked at Goldman Sachs and White Eagle Partners. Below you can see several examples of Mangrove Partners' activist campaigns.