Oh my god holy dammit I TOTALLY forgot about this. o_o
Aegislash!OVERPOWERED. One word sums up this Pokemon completely. Differing from a defensive and powerful form depending on moves used is an amazing feature for a competitive battler that knows how to use it properly. Being a Steel/Ghost type, it gets three immunities which already makes it a pain to the opponent if you switch it in at the right time.
The shield form has insane defenses, and can withstand many super effective attacks. The blade form has abismal defensive stats, but the attack is through the roof. It gets Swords Dance too if you want to double that attack, making it nearly unstoppable with Priority Shadow Sneak. Since the blade form can hold the middle finger up at most attacks, having the Weakness policy item increases the attack and special attack stats by 2 stages, usually without Aegislash fainting. After Weakness Policy activates and Swords Dance is used, you have yourself an insane sweeper, right there, when given Iron Head/Sacred Sword and Shadow Sneak.
Not much can defeat Aegislash in a hurry.