Is possible get Multiscale Dragonite with ExtremeSpeed without transferring the ExtremeSpeed Dragonite from HG/SS to BW2? Are there any other Pokemon with ExtremeSpeed available for breeding?
No, since no Pokemon that learns Extreme Speed by level up is in the Dragon or Water 1 egg groups and you couldnt chain breed it because only the Dragonite evolution line gets Extreme speed by breeding.
