The meme originates from one specific scene of the 2012 horror-comedy movie The Cabin in the Woods.
The scene features a class of Japanese schoolchildren expelling a demon in the middle of the classroom, eventually turning it into a frog. The cut finishes by one of the girls holding up the frog, saying “The evil is defeated”.
This scene was clipped out and then uploaded on YouTube by user Brian Newby in 2013.
Two years later an animated GIF appeared on Tumblr with the little girl saying the now famously known sentence.
The evil is defeated GIF became popular being utilized as a reaction meme, as it could be applied in any good-bad conflict where the good is victorious.
The meme since then has made appearances on Reddit, Twitter, Tumblr and all the other popular social media platforms.