@Pokefan_1987 If you're still looking for help I know of two Mons that can steamroll Volo AND Giratina through their STAB alone: Gardevoir and Rhyperior. Gardevoir's Moonblast clobbers Spiritomb, Garchomp, and Giratina itself while Psychic will help crumple Roserade. Rhyperior's Rock Slide/Stone Edge can crush Togekiss and H-Arcanine while High Horsepower will flatten Lucario and especially H-Arcanine. And that's before factoring in some coverage moves. Giving Gardevoir Mystical Fire and Thunderbolt will allow it to take down Lucario and Togekiss, respectively, while giving Rhyperior a combo of Shadow Claw, Poison Jab, Fire Punch, Aqua Tail, and/or Ice Punch can expand the range of its victims (specifically, Giratina with Shadow Claw and Ice Punch, Garchomp with Ice Punch, Togekiss with Poison Jab and Ice Punch, Roserade with Fire/Ice Punch, Lucario with Fire Punch, and H-Arcanine with Aqua Tail). Those two Mons alone can pretty much cover Volo's entire team and Giratina single-handedly. I wouldn't recommend using Legendaries like Darkrai and Cresselia, as they'll crumple to certain moves surprisingly quickly, especially against Giratina itself (Giratina has Aura Sphere to handle Darkrai and Shadow Force for Cresselia, the latter of which will further hamper any attempts to strike back due to the move "obscuring" it, making it harder to hit). Hope that helps.