Arceus-Fighting is one of the best offensive checks to Arceus of all Arceus formes and can also deal with threats such as Mega Lucario, Mega Gyarados, Dialga, Tyranitar, Arceus-Dark, Darkrai, and Arceus-Rock competently. While Arceus-Fighting is weak to Flying- and Psychic-type moves, it can use these weaknesses to its advantage by luring in and removing or heavily damaging its checks, such as Mega Salamence, Rayquaza, Lunala, and Ho-Oh. Unfortunately, Arceus-Fighting has a slew of fundamental issues that make it unviable in the Ubers metagame. Its defensive typing is dreadful, leaving it extremely vulnerable to dangerous Fairy-types, such as Xerneas and Arceus-Fairy, and rendering its effectiveness as a lure heavily reliant on good prediction. What would be a useful resistance to Dark is sullied by the fact that the most common Dark-type in Ubers, Yveltal, possesses a secondary Flying typing; being unable to deal with the best Dark-type in the tier cuts heavily into Arceus-Fighting's defensive use. Arceus-Fighting's offensive typing is also terrible. Ghost-types are immune to its STAB Judgment, while Fairy-, Flying- and Psychic-type Pokemon resist it, forcing Arceus-Fighting to rely on weak coverage moves and further increasing the need for flawless prediction when using it lest it give the opponent free turns. Arceus-Fighting also has bad four-moveslot syndrome; it wants to run Recover to act as a more durable check to Arceus, but it is instead often forced into running Shadow Ball so that it is not completely walled by Ghost-types. The main reason for Arceus-Fighting's utter lack of viability, however, is the fact that it is outclassed by Mega Lucario and Marshadow. Mega Lucario is not as bulky as Arceus-Fighting, but it is much stronger, can deal with Xerneas with its Steel-type STAB moves, and has a superior matchup against bulkier teams while maintaining usefulness against offense. Marshadow invalidates Arceus-Fighting even further, as it is a far better Arceus check due to its superior Speed, immunity to Extreme Speed, and ability to OHKO Arceus; Marshadow also has an excellent offensive typing and greater power, giving it far more utility against multiple playstyles. Additionally, neither of these Pokemon carry the downside of taking up a team's Arceus slot that Arceus-Fighting does. Due to this, Arceus-Fighting is a total waste of a team's Arceus slot and should not be considered for a serious team.
name: Offensive Utility
move 1: Judgment
move 2: Ice Beam
move 3: Stone Edge
move 4: Shadow Ball / Recover
item: Fist Plate
evs: 252 SpA / 4 SpD / 252 Spe
Judgment is Arceus-Fighting's best STAB move, cleanly OHKOing Tyranitar, Mega Tyranitar, and Mega Lucario and OHKOing Arceus, Arceus-Dark, and Dialga after some prior damage. Ice Beam allows Arceus-Fighting to lure in and damage Flying-types; it OHKOes Mega Salamence and Rayquaza and 2HKOes Yveltal. Stone Edge is run solely for Ho-Oh, OHKOing it after one round of Stealth Rock damage. Shadow Ball 2HKOes healthy Lunala, Marshadow, and Mega Gengar and deals good damage to Arceus-Ghost, ensuring Arceus-Fighting is not setup fodder for Ghost-types. Recover lets Arceus-Fighting take advantage of the few switches it forces and regain health, allowing it to repeatedly check Arceus throughout a match, but opting for it over Shadow Ball leaves Arceus-Fighting vulnerable to every viable Ghost-type in Ubers.
Maximum Special Attack investment makes Arceus-Fighting as strong as possible, while maximum Speed investment and a Timid nature let Arceus-Fighting Speed tie at worst with Mega Salamence as well as Speed tie with maximum Speed Arceus formes. The four Special Defense EVs ensure Genesect will receive an Attack boost upon switching into Arceus-Fighting, allowing Arceus-Fighting to better deal with it.
Switch Arceus-Fighting into Pokemon that it walls, such as Arceus-Dark, Arceus-Rock, and Tyranitar; this gives Arceus-Fighting a free turn more often than not by forcing the opponent to switch out and generates momentum for its team. In general, however, only switch Arceus-Fighting in after a teammate has fainted, as keeping it at high health is important; this is especially important if it isn't running Recover. If Arceus-Fighting's forme has been revealed, predicting what the opponent will do becomes even more difficult, as they will often have a foolproof way of removing it, such as Z-Geomancy Xerneas; play it very safely in this situation. If running Recover, it is important to judge whether or not it is worth risking the opponent switching out into a check on the Recover and eliminating any momentum Arceus-Fighting has gained. Arceus-Fighting can be played aggressively against bulkier teams, as its weak coverage moves and vulnerability to all status leave it with a terrible matchup against them, so do not be afraid to sacrifice it when needed.
Primal Groudon can set up Stealth Rock and check Fairy-types for Arceus-Fighting. Swords Dance + Stealth Rock variants are generally best as teammates so as to better deal with Z-Geomancy Xerneas. Choice Scarf Lunala appreciates Arceus-Fighting's ability to remove Arceus-Dark and can deal with Ghost-types in return. Alolan Muk and Tyranitar can Pursuit trap Ghost- and Psychic-types for Arceus-Fighting, while the former can also check Xerneas. Note that Tyranitar adds an extra Fairy weakness to Arceus-Fighting's team, which can be troublesome. Yveltal can perform a similar role by using its excellent offensive capabilities to pressure Arceus-Fighting's checks, but it has the same issue as Tyranitar. Xerneas and Mega Salamence benefit from Arceus-Fighting's ability to beat most Steel-types; Xerneas also appreciates Arceus-Fighting's ability to remove Ho-Oh and can act as a soft check to Marshadow in exchange. Frail attackers such as Deoxys-A greatly benefit from Arceus-Fighting's ability to check Extreme Killer Arceus. Mega Gengar can beat Clefable and certain Xerneas variants while absorbing Toxic Spikes; Arceus-Fighting can beat some of the Dark-types that threaten Mega Gengar, such as Arceus-Dark, in return.
An offensive Calm Mind set with Fightinium Z + Focus Blast gives Arceus-Fighting a one-time 190-Base Power All-Out Pummelling which, at +1, can OHKO specially defensive Primal Groudon after Stealth Rock and do a good chunk of damage to Geomancy Xerneas. However, Arceus-Fighting's terrible defensive typing makes a Calm Mind set very unappealing; additionally, it forces Arceus-Fighting to give up a coverage move for Calm Mind and possibly another coverage move if Recover is run, which makes Arceus-Fighting even easier to check than it already is. Sludge Bomb hits Xerneas and Arceus-Fairy, but standard Geomancy Xerneas requires some prior damage to be 2HKOed, while Arceus-Fairy needs to take Stealth Rock damage and be poisoned on the switch before a 2HKO is even a possibility, making Sludge Bomb a suboptimal choice. Thunder Wave can cripple Mega Gengar on the switch but is impossible to fit. Defog sets can defeat Ferrothorn and Dialga but are very passive; this, combined with Arceus-Fighting's bad defensive typing for a support Pokemon, makes it impossible to justify using Defog on Arceus-Fighting.
Checks and Counters
**Fairy-types**: Xerneas, Arceus-Fairy, and Clefable completely wall Arceus-Fighting, as they resist its STAB move and take very little damage from its best coverage moves. Magearna is only at best 3HKOed by Judgment, which means it can easily switch into Arceus-Fighting and OHKO it with Fleur Cannon after some prior damage.
**Poison-types**: Tentacruel, Toxapex, and Arceus-Poison resist Judgment and are not hit super effectively by Arceus-Fighting's coverage moves, allowing them to set up on it.
**Ghost-types**: Ghost-types are immune to Judgment, forcing Arceus-Fighting to make use of its weak coverage moves. Giratina takes very little damage from Ice Beam and can use Arceus-Fighting as Defog bait. Arceus-Ghost is not 2HKOed by Shadow Ball after Stealth Rock, allowing it to potentially do massive damage to Arceus-Fighting. If Arceus-Fighting lacks Shadow Ball, Mega Gengar, Aegislash, Marshadow, and Lunala become very potent answers to it. Mega Gengar outspeeds and traps Arceus-Fighting. Aegislash walls Arceus-Fighting and can Toxic stall it. Marshadow cannot switch into Arceus-Fighting but does more damage with Close Combat than Recover can heal, which can force trades. Choice Scarf Lunala 2HKOes Arceus-Fighting with Psyshock, while Calm Mind variants can use it as setup fodder.
**Psychic-types**: Mega Mewtwo Y and Choice Scarf Tapu Lele outspeed Arceus-Fighting and OHKO it with Psystrike and Psychic, respectively. Deoxys-A cannot switch into Arceus-Fighting but can easily revenge kill it with Psycho Boost.
**Flying-types**: While most Flying-types fear one or two of Arceus-Fighting's coverage moves and thus cannot switch in, some Flying-types can deal with it regardless. Lugia is bulky enough to shrug off Ice Beam, even if Multiscale is broken, and can Toxic stall Arceus-Fighting. Choice Scarf Yveltal can switch into Ice Beam if Stealth Rock is not up, outspeed Arceus-Fighting, and 2HKO it with Oblivion Wing.
**Bulky Pokemon**: Most bulky Pokemon can easily deal with Arceus-Fighting, as it is quite weak. Arceus-Water, Arceus-Dragon, defensive variants of Arceus-Ground, Buzzwole, Mega Sableye, Blissey, and Chansey are all bulky enough to take whatever Arceus-Fighting can throw at them and Toxic stall it. Defensive Primal Kyogre walls Arceus-Fighting and 2HKOes it with Primordial Sea-boosted Scald most of the time.