Fairy Tail Episode 167: 100 Against 1
Episode 167 of 175 of Fairy Tail, aired February 1, 2013, 25 minutes. Available with English subtitles and dub where released.
Episode summary
In the event called Pandemonium, Erza has opted to take on 100 powerful magic-generated monsters by herself... but what is the secret of the one S-class monster?!