Moves
Nasty Plot boosts Hoopa's Special Attack, allowing it to break common cores. Shadow Ball is its main attack, hitting most of the tier for neutral damage, as well as becoming immensely powerful when used with Ghostium Z. Focus Blast has great neutral coverage in conjunction with Shadow Ball, hitting frailer Ghost-type resists for large amounts of damage, and with Fightinium Z, Hoopa can break defensive Dark-types such as Alolan Muk and Umbreon after minimal prior damage, as well as Blissey. Substitute gives safer setup opportunities and prevents Hoopa from being worn down by status conditions, and it can be used on a free turn or on a forced switch. Psyshock can be used over Substitute to break bulky Pokemon like Blissey and Calm Mind Suicune harder, but this makes Hoopa easily revenge killed by common Pursuit users like Krookodile and Mega Aerodactyl.
Set Details
Maximum investment in Special Attack and a Modest nature give Hoopa as much power and breaking potential as possible. 252 Speed EVs let Hoopa outspeed threats such as Scizor, Crawdaunt, and most defensive Pokemon such as Mantine and defensive Togekiss. 4 Special Defense EVs are used so unboosted Suicune never breaks Hoopa's Substitute. A Timid nature can be used to outspeed Primarina, but since at +2, Modest Hoopa has a 50% chance to OHKO Alolan Muk after Stealth Rock and a Nasty Plot boost, Modest is the preferred option. Fightinium Z is the more viable item option, allowing Hoopa to muscle past common checks to Psychic-types such as Alolan Muk and Blissey while being a no-drawback move to OHKO Krookodile and Hydreigon. Ghostium Z allows Hoopa to severely dent neutral switch-ins with its excellent power and break defensive cores more readily at the cost of being unable to KO Alolan Muk and Blissey reliably. Alternatively, Life Orb can be used if another teammate utilizes the Z-Move better or if running an all-out attacker set.
Usage Tips
Do not try to set up until Pursuit trappers like Choice Band Scizor are have been weakened and faster Pokemon like Hydreigon have been KOed. Take advantage of Hoopa's good special bulk by using Pokemon such as -2 Latias, bulky Water-types, and resisted attackers as setup fodder. Additionally, forcing switches also gives free setup opportunities. Use Hoopa's Ghost typing to block Rapid Spin from weaker spinners such as Tentacruel, but not offensive ones like Mega Blastoise and Starmie, which can overpower Hoopa quite easily, and use Substitute on weaker or resisted special attackers like Suicune, as this can help alleviate pressure from incoming Pursuit trappers, as well as avoid being hit by a potentially damaging status effect. Try to keep Hoopa healthy versus bulkier teams, as its power to break through walls such as Mega Aggron, Alomomola, and Blissey is extremely useful. Steel-types such as Cobalion and Scizor also are good targets of the Z-Move if opposing Dark-types have been chipped down or KOed. Never-Ending Nightmare should be used as soon as opposing Dark-types are heavily damaged, as most teams do not have switch-ins to it. Due to Hoopa's lack of recovery and need to set Substitute, try to pivot into it in via U-turn, Volt Switch, or a sacrifice.
Team Options
Hoopa fares well on offensive builds that appreciate its wallbreaking capacity. Klefki makes an excellent partner, as it can set entry hazards to weaken checks, as well as slow down faster teams with Thunder Wave to ease a sweep, and in return, Hoopa can block Rapid Spin. Stealth Rock setters such as Nihilego, Krookodile, and Cobalion also weaken checks and appreciate Hoopa's spinblocking. Other powerful special attackers like Latias, Mega Manectric, and Hydreigon enjoy Hoopa's ability to break past common checks such as Blissey and Alolan Muk. Checks to Dark-types, such as Mega Altaria, and Cobalion, help Hoopa by alleviating offensive pressure on it, provided you play aggressively. Fast Pokemon such as Mega Aerodactyl and Choice Scarf Hydreigon can help make up for Hoopa's lack of Speed. Hazard removers such as Tentacruel, Gligar, and Rotom-H are good teammates because Hoopa is less effective once it has taken residual damage. Wallbreakers such as Infernape and Scizor appreciate Hoopa's ability to weaken defensive Pokemon that they struggle with. Pokemon that resist Dark- or Ghost-type attacks such as Krookodile and Terrakion make good teammates due to their ability to take hits such as Knock Off from opposing Krookodile and Shadow Ball from Gengar.