According to Official Guinness Records,
The fastest average time to solve a Megaminx (Rubik's Cube) is 35.15 seconds and was achieved by Juan Pablo Huanqui Andia (Peru), at the Latin American Cubing Tour 2017, in Santiago, Chile, on 11 June 2017. During Juan Pablo's attempt he also broke the record for the fastest time to solve a Megaminx, solving the puzzle in only 29.93 seconds.
For a complete list of 2017 records, please visit 2017 Guinness Records in Chile.