Moves
Hidden Power Electric allows Combusken to OHKO Swanna and 2HKO Qwilfish, which both resist its STAB moves. Substitute can be run instead to allow Combusken to punish switches and protect itself from Pokemon such as Dodrio and Carracosta that would otherwise revenge kill it, gain extra Speed boosts, and stall poisoned Pokemon. Protect allows Combusken to get a free Speed boost and scout Choice item Pokemon such as Primeape, Dodrio, and Aurorus.
Set Details
Firium Z lets Combusken OHKO Oricorio-E with Inferno Overdrive after Stealth Rock damage; furthermore, Inferno Overdrive has a high chance to OHKO Skuntank and Alolan Raichu and hits targets such as Mudsdale and Musharna that would otherwise force Combusken out for as much damage as possible, KOing both after Fire Blast and Stealth Rock. Fightinium Z is an alternative that allows Combusken to OHKO Regirock and Drampa with All-Out Pummeling, do greater damage to Pokemon such as Lanturn, and bypass Focus Blast's poor accuracy once. Leftovers is an option that allows Combusken to set up more Substitutes while staying out of range of priority users such as Gurdurr and Lycanroc more easily; however, this should only be run on sets featuring Substitute, as three attacks sets benefit more from the extra damage Z-Crystals offer. Life Orb is an option on teams not using Toxic Spikes if another Pokemon is holding a Z-Crystal, helping to make up for Combusken's average damage output, such as offering it a high chance to OHKO Regirock with Focus Blast. The chip damage makes Combusken have a harder time staying out of range of priority attacks such as Lycanroc's Accelerock, however.
Usage Tips
Combusken should avoid taking too much chip damage from entry hazards and status where possible and should mainly be brought in via safe switches and aggressive double switches so it can stay out of range of priority attacks such as Gurdurr's Mach Punch and Lycanroc's Accelerock to reliably clean late-game. Combusken can also be used early- to mid-game to immediately pressure teams and take advantage of switches to counters such as Jellicent with appropriate double switches. If running Substitute, Combusken can use it to punish switches it forces against Pokemon such as Ferroseed, Cryogonal, Tangela, Alolan Sandslash, and Victreebel, although it must be careful when doing this against the latter two, as they can outspeed and either cripple or KO Combusken if they predict it to use Substitute. Against more offensive teams, Substitute can help ease prediction and make Combusken harder to revenge kill while helping it outspeed Pokemon such as Choice Scarf Dodrio and Primeape that it needs multiple Speed boosts for. Combusken should, however, be wary of setting up too many Substitutes when counters such as Carbink and Altaria are present, especially when running a Z-Crystal instead of Leftovers, so it has enough HP to take priority attacks or keep setting up Substitutes later in the match. If a teammate is running Toxic Spikes, Combusken can very effectively poison stall with Substitute + Protect, as Speed Boost allows it to nearly always set up Substitutes first. In particular, this allows Combusken to pressure Jellicent a lot more, forcing it to take poison damage while attempting to force Combusken out with Taunt.
Team Options
Combusken fits on bulky offense and balance teams that desire a late-game cleaner and on Toxic Spikes teams where it can also function as a poison staller. Pivots such as Lanturn, Eelektross, and Silvally-Fairy can help bring Combusken in on Pokemon that it can force out such as Victreebel, Cryogonal, and Regirock, offering it free opportunities to gain Speed boosts, set Substitutes, or break the enemy team. Lanturn and Eelektross in particular can help pressure Jellicent, and Lanturn can also help to spread poison onto Pokemon that annoy Combusken such as Jellicent, Eelektross, and opposing Lanturn and clear Combusken of status with Heal Bell. Pokemon that can help deal with Jellicent in particular are incredibly useful, especially when you're not running it alongside Toxic Spikes. Victreebel can consistently switch into and pressure defensive Jellicent while switching into and helping break other Pokemon such as Gurdurr and Mudsdale that can force Combusken out when at high HP, as well as help break through Carbink and Clefairy, which can otherwise wall Combusken. Pokemon such as Choice Band Stoutland and Absol are capable of Pursuit trapping Jellicent and can help pressure the special walls that Combusken dislikes, such as Lanturn, Eelektross, and Musharna. Wallbreakers such as Choice Specs Aurorus, Taunt Oricorio-E, Golurk, and Swords Dance Silvally-Fairy can also help to break through specially defensive Pokemon such as Altaria, Carbink, and Clefairy that can consistently wall Combusken, as well as break holes in the enemy team for Combusken to reliably clean late-game.
Toxic Spikes support from Pokemon such as Qwilfish and Roselia can help Combusken break through opposing teams via stalling through the combination of Substitute + Protect, allowing it to more easily beat Pokemon such as Assault Vest Lanturn that would otherwise give it a lot of trouble. Roselia is able to consistently pressure Jellicent alongside setting Toxic Spikes, which is helpful in matchups against grounded Poison-types such as Victreebel or against entry hazard removers that Roselia loses to such as Cryogonal, while Qwilfish is able to provide a switch-in to priority users such as Hitmonchan and Gurdurr that could revenge kill Combusken, as well as to Choice Scarf Dodrio, which can outspeed Combusken after multiple Speed boosts. Spinblockers such as Jellicent and Sableye are excellent partners, especially on Toxic Spikes teams, to help deal with Rapid Spin users such as Alolan Sandslash, although they have to be wary of Toxic. Sableye can also offer Knock Off support to aid Combusken in poison stalling foes, while both Pokemon can help check Fighting-types such as Hitmonchan and Primeape and offer Taunt support to pressure entry hazard setters and removers.