Attack or Special Attack. Sorry I forgot to add the Non-Legendary thing. Psuedo-legendary Pokemon don't count, and neither does cresselia, heatran, etc.
Deoxys-Attack, who has 330 BST when Attack/Special Attack (won't matter which one, they are both base 180) and Speed are combined.
Not including legendaries, it is Slaking, with 260 BST (160 in Attack, 100 in Speed). Slaking does not qualify as a pseudo-legendary since Truant essentially kills its viability.
It would be Alakazam, weavile, Haxorus (not the best speed but its good) and scyther