Sworn enemy.

Cursed Enemy is useful against any race. It’s just used differently. For example, against Haven or Gnomes with their good defense, Cursed Enemy + Rain + Enchanted Arrow + Chaos + New Druids = good chances of winning (if you take the Fire Lord, the fire spells will also remove 50% of the armor). Against Dungeon or Academy, Cursed Enemy is needed to quickly eliminate enemy troops, so as not to allow the enemy Hero to severely damage you with magic. So, it should be upgraded regardless of the opponent; it is real help in battle.