 If you liked
Juuou Mujin no Fafnir
|
 ...then you might like
Yuuki Yuuna wa Yuusha de Aru
|
Both animes are about innocent girls teaming up to fight a limited number overwhelmingly powerful enemies that require a lot of planning, strategy, effort, and risk to take down.
Enemies tend to appear one at a time and each have their own "gimmick" that makes them sound almost impossible to kill, such as only being able to kill 3 enemies if you strike them all at the same time so they can't regenerate, or an enemy that's made of air and is impervious to most attacks.