Well I would have to say Night Elves if used right they could completely weakened the enemy forced using Faerie Fire or even the Dryad's poison attack, the Night Elves is followed closely by the Undead, the Undead kills the opponent by overwhelming the enemy by massing ghouls which are the cheapest first-tier unit and the Frost Wyrm are just plain powerful. 3rd Place goes to the Orcs just for the fact that they're just plain powerful I mean one of the most feared magical combos are created by the orcs imagine a group of bloodlusted Grunts which is supported by a healing ward. So overall I would have to say that all the races have their very own unique skill but personally I think that 1st place belongs to the Night Elves.