>>23137246252+ Atk Life Orb Bisharp Sucker Punch vs. 0 HP / 0 Def Giratina-O: 367-432 (83.2 - 97.9%) -- 62.5% chance to OHKO after Stealth Rock
Not trying to prove you wrong, but it needs a little passive damage for it to work.
Also, lrn2metagame, Offensive Gira-O will use some bulk, as it has no need to fully invest on speed (at worst, 96 Spe, to outspeed... Bisharp)
That means:
252+ Atk Life Orb Bisharp Sucker Punch vs. 0 HP / 160 Def Giratina-O: 312-369 (70.7 - 83.6%) -- guaranteed 2HKO after Stealth Rock
252+ Atk Life Orb Bisharp Sucker Punch vs. 160 HP / 0 Def Giratina-O: 367-432 (76.2 - 89.8%) -- 18.8% chance to OHKO after Stealth Rock
Needless to say...
252+ SpA Giratina-O Aura Sphere vs. 4 HP / 0 SpD Bisharp: 488-576 (179.4 - 211.7%) -- guaranteed OHKO
On the other hand...
252+ SpA Giratina-O Aura Sphere vs. 248 HP / 252 SpD Assault Vest Tyranitar in Sand: 132-156 (32.7 - 38.7%) -- 98% chance to 3HKO
