**for Season 4.2 update**
With the achievements being changed this is now earn 5 Flawless victories in ranked following the 4.2 Phantom Sight update. All this means is you have to WIN 5 Full games (not rounds) 4-0'ing the other team. This means you Win 4 rounds in a row. While possible in solo que, I recommend having at least 2-3 other teammates so that you can communicate to win.