Prototype (Ar tonelico II: Melody of Metafalica)

Slightly edging out the Type 888 as second strongest Robot-type monster, the Prototype is much more powerful than its predecessors not only due to its stats, but also because of the danger its attacks suppose. Aside of the classical K-BLADE and the single-hitting D-PIERCE single target attacks, it can also use the triple hitting P-AZMA, and it also gained a new attack called S-RAIN which hits a party member four times. This alone allows it to deal a large amount of damage on each Defense Phase it gets, so it is advisable to defeat it quickly and to be careful when it's time to block its attacks.