I have a couple sets that could potentially be good in VGC and Singles.
Koraidon @ Assault Vest
Impish Nature
Ability: Orichalcum Pulse
EVs: 252 HP / 148 Def / 108 SpD
- Collision Course
- Drain Punch
- Breaking Swipe
- Fire Fang / Iron Head / Snarl
This Koraidon set would be for VGC.
No exact reasoning for the Def and SpDef EV values, just to invest in them slightly evenly. Collision Course, is insane. 100 BP, 100% Accuracy, and bonus damage if the move is super effective when used. When you combine that with base 135 Atk, and a +1 Atk from your ability, it can even put a dent in Pokémon that resist it. Fire Fang is (I believe) the strongest physical fire move that it gets without recoil, but it still can hit quite hard considering Koraidon sets up his own sun, and gets +1 because of his own sun. Drain Punch is a good recovery option, and Breaking Swipe / Snarl are mainly for disrupting, and Iron Head is good coverage against fairies and ice types.
Chien-Pao @ Heavy-Duty Boots
Jolly Nature
Ability: Swords of Ruin
EVs: 252 Atk / 4 SpD / 252 Spe
- Icicle Crash
- Sucker Punch / Crunch
- Sacred Sword
- Swords Dance
This Chien-Pao set would be for 6v6 singles
This Pokémon is insane, even after the nerf. I wouldn’t be surprised if it gets quick banned to Ubers. I can’t even begin to think what was going through their mind when they made this Pokémon. Chien-Pao threatens late game sweeps simply by existing. It can come in via slow pivot moves, or after a teammate dies, and force out switches because everything will be -1 Defense. If the situation allows for it, you can then instead use Swords Dance, predicting a switch.
If the ability is actually an aura, and not a stat debuff, you’re effectively at +2 Atk with your opponent being -1 Def after a swords dance. Icicle Crash is standard, and you can run Crunch for more STAB coverage. Alternatively, you can run Sucker Punch to be less threatened by Choice Scarf users, or faster Pokémon. Sacred Sword will probably be the most popular non-STAB, coverage move, but there are some other notable options, such as Psychic Fangs, or even Aerial Ace. One possibility is that Ice Spinner might be an option over Icicle Crash, but I am not aware of the accuracy or BP of the move.
Miraidon @ Life Orb
Timid Nature
Ability: Hadron Engine
- Electro Drift
- Volt Switch
- Draco Meteor
- Flash Cannon / Overheat
This would be for 6v6 singles.
The Zacian nerf seems really weird because these Pokémon exist. It seems like they listened to complaints on how broken Zacian is, nerfed it, then completely threw logic out th window and then made Koraidon and Miraidon.
Without a doubt, Miraidon benefits more from the terrain it sets up compared to Koraidon with its sun. You get 100/100/115 bulk, 135 Sp.Atk, and 135 Speed. If that wasn’t already insane, you get Electric Terrain, making one of your STABs even stronger, and +1 Sp.Atk. Koraidon is still broken, but at least sun doesn’t boost one of their STAB options.
Electro Drift and Draco Meteor are basically instant nukes. Volt Switch makes it hard to get a good hit in on Miraidon, while still hitting insanely hard in the process. Flash Cannon is probably the best coverage option, considering you can hit fairies and ice types for super effective damage. Alternatively, you can use Overheat paired with a sun setter, such as Koraidon (oh my god).
I apologize if the post is not worded properly. I don’t usually make these types of posts, or at all really. I just wanted to state the obvious and describe how truly strong these new Pokémon are.