Which is the most powerful supercomputer in the world currently?

Tianhe-2
According to a biannual Top500 list of supercomputers, China’s Tianhe-2 supercomputer has maintained its position as the world’s most powerful system for the 6th consecutive time. Tianhe-2 (or Milky Way 2) was developed by China’s National University of Defence Technology and deployed at the National Supercomputer Center in Guangzhou. Its performance is 33.86 petaflops per second (Pflop/s), .It has held the title since June 2013. The Chinese system is almost twice as fast as the next on the list, Titan of the US Department of Energy