Something I've seen talk about is how Milotic is the counterpart of Gyarados, a Generation I Pokémon, who shares the same physical shape as Milotic. From what I've read I am inclined to agree. I will go on to explain why that is, and throw in my own nickle (pennies don't exist here anymore) about it.
Now, if for some reason you are unfamiliar with Gyarados (what rock have you been living under?) it is a Generation I Pokémon that made its debut in Pokémon Red/Blue (Pokémon Red/Green in Japan) for the Nintendo Gameboy. It is known as the Atrocious Pokémon and is the final evolution form of Magikarp, a generally weak and pathetic Pokémon. Gyarados has a thing for destroying things and is generally attracted to violence, oftentimes going on a wild rampage. So how does all this make it any kind of counterpart to Milotic? I'm coming to that next.
First off, both Pokémon have serpent-like appearances, and share physical similarities. However, these two Pokémon act very differently from each other, making Milotic more of the opposite of Gyarados. While both Pokémon will appear in times of conflict, Gyarados promotes violence, while Milotic instead calms any violent feelings one might have. Also, like Gyarados, Milotic evolves from a weak and pathetic Pokémon into something more powerful and generally more awesome. Also, these two have the same base stat total of 540, although their Attack, Special Attack and Special Defense stats are spread out differently between the two, further showing what each one would represent. Gyarados being power, and Milotic being beauty.