Ok so personally i think mirajane is. Why because 1. She has three powerful take-overs. 2. She's very durable abd 3. She's juss awesome. Dont take me wrong Erza has a few nice tricks like her armors , but mirajane is a demon, a real demon. She has a variety of attacks that range from electricity to fire to water to darkness and so on. So tell me yall opinions.