Arceus-Flying @ Sky Plate
Ability: Multitype
EVs: 252 HP / 4 SpA / 252 Spe
Timid Nature
- Calm Mind
- Judgment
- Flamethrower
- Recover

Necrozma-Dusk Mane @ Weakness Policy
Ability: Prism Armor
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Dragon Dance
- Sunsteel Strike
- Earthquake
- Photon Geyser

Kyurem-White @ Choice Scarf
Ability: Turboblaze
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Draco Meteor
- Ice Beam
- Earth Power
- Fusion Flare

Kyogre-Primal @ Blue Orb
Ability: Drizzle
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Origin Pulse
- Ice Beam
- Water Spout
- Thunder

Groudon-Primal @ Red Orb
Ability: Drought
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Rock Polish
- Precipice Blades
- Heat Crash

Rayquaza-Mega @ Life Orb
Ability: Air Lock
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Dragon Dance
- Dragon Ascent
- Outrage
- Extreme Speed

Some notes:
* Change Arecus's plates around a lot. I posted a set with Sky Plate but get ready to use some other plates like Zap (Electric), Fist (Fighting), Flame (Fire), etc. You may also change the coverage move (Flamethrower) just in case before some battles, but keep Calm Mind, Judgment, and Recover.
* Kyurem-W's Choice Scarf may be vital for revenge kills and whatnot, but Icium Z is really necessary for it in Big Mo and Tessy.
* The Hoenn legendaries are necessary to disrupt the special weather against Mirskle (Fog), Alice (tailwind + Delta Stream), and Tessy (heavy rain). Mega Rayquaza can hold very item and there is no mega stone for it; it can mega evolve as long as it knows Dragon Ascent.
* Necrozma-DM is a key member since its Prism Armor allows it to lower the damage from super-effective attacks. With Weakness Policy and Dragon Dance it can become the ultimate killing machine.
* Note also that Mirskle and Galavan battles are double, so watch out for them too.
* To get Necrozma-DM you may need N-Solarizer, and Marshadow will hold it if you redeem its code in the postgame. After getting it, fuse your Necrozma and Solgaleo using this item to form Necrozma-DM.
* To get Kyurem-W, you need DNA Splicers, and Genesect will hold it if you redeem its code in the postgame. After getting it, fuse your Kyurem and Reshiram using this item to form Kyurem-W.
* Finally, note also that some of the mons may be inaccurate (I may run Surf in Kyogre just to not mess with the inaccurate Origin Pulse, for instance). I have not played Unbound for around seven months, so I wrote some of the moves from memory.