This is an interesting question because it entirely depends on your training and fitness level. Every stroke has its technical nuances, but Butterfly is certainly the hardest stroke to get right. read more
Like most answers you have seen butterfly and breaststroke are the hardest, but that doesn't apply to everyone. If you feel uncomfortable on your back while swimming, backstroke could be your hardest stroke. Some people have a hard time at freestyle, but are amazing in breast stroke. read more
Even if you are evaluating strokes based on how difficult they are to swim properly, some coaches argue that breaststroke is harder to master than the other so-called short-axis stroke, the butterfly. read more