Some sets I thought of:
Kyogre @ Blue Orb
Ability: Shell Armor (Primordial Sea)
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Shell Smash
- Surf / Hydro Pump
- Ice Beam
- Earth Power
Inherits from Omastar. Once the Extreme Speed users are down, this set is insane. Shell Smash fixes Kyogre's low Speed and takes its Special Attack to insane new heights. Surf is the STAB move, although Hydro Pump can be used if you want more power. Ice Beam hits the Grass and Dragon types that resist Surf. Earth Power OHKOes any primal Groudon. EVs give you enough Speed to outrun Scarf Terrakion at +2, but you could run more Speed or bulk depending on your preferences.
Regigigas @ Life Orb
Ability: Sheer Force
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature / Adamant Nature
- Rock Climb
- Sucker Punch
- Earthquake / Gunk Shot / Rock Slide
- Earthquake / Gunk Shot / Rock Slide
Inherits from Druddigon. Rock Climb gets STAB and a Sheer Force boost, hitting for almost the same power as Double-Edge. Sucker Punch gives you priority. The last 2 slots are a toss up: Earthquake hurts bulky Rock and Steel types, but doesn't get a Sheer Force boost; Gunk Shot wrecks Xerneas; Rock Slide wrecks Ho-Oh. EVs maixmise Speed and Attack
Palkia @ Lustrous Orb
Ability: Adaptability
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature / Modest Nature
- Draco Meteor
- Hydro Pump
- Surf
- Focus Blast
Inherits from Dragalge. Draco Meteor is your most powerful STAB, hitting for an insane 260 power with Adaptability. Hydro Pump has no stat penalties although has shaky accuracy - it hits for a might 220 power with Adaptability. Surf is a reliable STAB for when you don't want to risk a miss. Focus Blast wrecks Ferrothorn, the only Pokémon which resists your STAB combination. EVs maximise Speed and power. Most of the time you'll be spamming your STABs, so Lustrous Orb is the best item to use.
Dialga @ Life Orb
Ability: Sheer Force
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Rock Polish
- Flash Cannon
- Earth Power
- Ancient Power / Fire Blast
Inherits from Mega Camerupt, this set is meant to sweep late game. Dialga's niche is not being weak to any form of priority bar Mach Punch and Vacuum Wave, neither of which are especially common. Rock Polish fixes its low Speed, giving enough to outrun Scarf Terrakion with this spread (although more Speed or bulk can be used depending on your preferences). Flash Cannon gets STAB and a Sheer Force boost, hitting about as hard as a STAB Return. Earth Power OHKOes 252/200 Relaxed Primal Groudon after Stealth Rock; physically defensive or offensive variants are OHKOed. Ancient Power OHKOes 248/52 Ho-Oh after any residual damage, while Fire Blast hits much harder and can be used to take out Ferrothorn. I should point out that this set needs to have Kyogre and most special walls down.
Kyogre @ Blue Orb
Ability: Shell Armor (Primordial Sea)
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Shell Smash
- Surf / Hydro Pump
- Ice Beam
- Earth Power
Inherits from Omastar. Once the Extreme Speed users are down, this set is insane. Shell Smash fixes Kyogre's low Speed and takes its Special Attack to insane new heights. Surf is the STAB move, although Hydro Pump can be used if you want more power. Ice Beam hits the Grass and Dragon types that resist Surf. Earth Power OHKOes any primal Groudon. EVs give you enough Speed to outrun Scarf Terrakion at +2, but you could run more Speed or bulk depending on your preferences.
Regigigas @ Life Orb
Ability: Sheer Force
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature / Adamant Nature
- Rock Climb
- Sucker Punch
- Earthquake / Gunk Shot / Rock Slide
- Earthquake / Gunk Shot / Rock Slide
Inherits from Druddigon. Rock Climb gets STAB and a Sheer Force boost, hitting for almost the same power as Double-Edge. Sucker Punch gives you priority. The last 2 slots are a toss up: Earthquake hurts bulky Rock and Steel types, but doesn't get a Sheer Force boost; Gunk Shot wrecks Xerneas; Rock Slide wrecks Ho-Oh. EVs maixmise Speed and Attack
Palkia @ Lustrous Orb
Ability: Adaptability
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature / Modest Nature
- Draco Meteor
- Hydro Pump
- Surf
- Focus Blast
Inherits from Dragalge. Draco Meteor is your most powerful STAB, hitting for an insane 260 power with Adaptability. Hydro Pump has no stat penalties although has shaky accuracy - it hits for a might 220 power with Adaptability. Surf is a reliable STAB for when you don't want to risk a miss. Focus Blast wrecks Ferrothorn, the only Pokémon which resists your STAB combination. EVs maximise Speed and power. Most of the time you'll be spamming your STABs, so Lustrous Orb is the best item to use.
Dialga @ Life Orb
Ability: Sheer Force
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Rock Polish
- Flash Cannon
- Earth Power
- Ancient Power / Fire Blast
Inherits from Mega Camerupt, this set is meant to sweep late game. Dialga's niche is not being weak to any form of priority bar Mach Punch and Vacuum Wave, neither of which are especially common. Rock Polish fixes its low Speed, giving enough to outrun Scarf Terrakion with this spread (although more Speed or bulk can be used depending on your preferences). Flash Cannon gets STAB and a Sheer Force boost, hitting about as hard as a STAB Return. Earth Power OHKOes 252/200 Relaxed Primal Groudon after Stealth Rock; physically defensive or offensive variants are OHKOed. Ancient Power OHKOes 248/52 Ho-Oh after any residual damage, while Fire Blast hits much harder and can be used to take out Ferrothorn. I should point out that this set needs to have Kyogre and most special walls down.