Set Description
Spore is what sets Breloom apart from the other Fighting-types in OU. Sleep is a great asset against balance and defensive teams that have a dedicated role for each Pokemon, as putting one wall out of commission provides opportunities for specific teammates to wallbreak and sweep. For example, putting a Ground-, Water-, or Steel-type to sleep can help secure a Dragon Dance Tyranitar sweep. Spore is also good against hit-and-run-based offense teams that lack setup sweepers that are strong against Breloom, as these teams struggle to come back from the functional one Pokemon deficit of sleep. Spore is also useful to shut down Spikers and spinners like Skarmory, Claydol, or Forretress.
Focus Punch is Breloom's strongest move and synergizes perfectly with Spore, allowing it to dish out a devastating attack while the opposing Pokemon is sleeping or switching out. It is so strong that physically bulky Pokemon like Skarmory, Metagross, and Swampert are likely to be 2HKOed, common Fighting-resistant foes like offensive Zapdos and Moltres are potentially 2HKOed in sand, and even sturdier Fighting-resistant foes like Salamence cannot switch in forever. While not as powerful, Sky Uppercut is a reliable attack that threatens Tyranitar, Snorlax, and Blissey, which sometimes stay in on Breloom after a teammate has been put to sleep; Sky Uppercut is also useful to finish off slow Pokemon that Breloom or its teammates have weakened previously, like Skarmory, Swampert, and Metagross. The combined threat of Focus Punch on switching out and Sky Uppercut on staying in makes Breloom really hard to predict and appropriately check.
Mach Punch makes Breloom the best priority user in OU. Mach Punch primarily revenge kills chipped Dragon Dance Tyranitar and low HP Aerodactyl; additionally, it puts Dugtrio that revenge kill Breloom into range of Tyranitar's Pursuit. Finally, Mach Punch gives Breloom that extra bit of damage against many faster offensive threats like Jolteon, offensive Jirachi, Salac Berry Heracross, and Salac Berry Vaporeon, helping teammates take them down, possibly with the aid of sand, even if Mach Punch itself does not KO them.
A Jolly nature is preferred over Adamant to outspeed maximum Speed Tyranitar, Swampert, Cloyster, and Vaporeon; slower variants of defensive Celebi, Jirachi, and Zapdos; and neutral nature Metagross, Claydol, and Magneton. At worst, Jolly Breloom Speed ties with Metagross, Cloyster, and Magneton. Outspeeding maximum Speed Tyranitar is especially important because it commonly runs a set with Lum Berry and Fire Blast, which allows it to switch into Spore and OHKO Breloom. However, an Adamant nature gives a 50% chance to OHKO Modest Blissey with Sky Uppercut and a chance to 2HKO Skarmory with Focus Punch + Sky Uppercut.
There are generally two ways to use Spore. If Breloom is used on a team with a variety of sweepers and wallbreakers, it is beneficial to use Spore early-game. There is a good chance that Spore disables a check to one of Breloom's teammates, letting it make progress. If Breloom's team is focused on trading KOs with the opponent, such as a Dugtrio team or one with Choice Band Metagross and Curse + Self-Destruct Snorlax, then it is beneficial to use Spore late-game after several trades are made. This prevents opponents from sacrificing the sleeping Pokemon and increases Breloom's impact—with few Pokemon remaining, it is likely that the opponent will lack a sufficient defensive backbone to handle Spore and Focus Punch. While Spore is almost always good to use, one must be wary of getting lured into providing setup opportunities; sweepers like Dragon Dance Salamence and Calm Mind Jirachi can easily turn the tables if Breloom slept a different foe instead, bringing their team back from behind.
Team Options
The single most important piece of support that Breloom appreciates is Pursuit, since Gengar walls it and bulky Psychic-types like Celebi, Starmie, and Claydol check it effectively. Pursuit Tyranitar is an excellent partner that can potentially deal with all of these Pokemon. In addition, it traps the Flying types that threaten Breloom: Tyranitar can switch into Choice Band Salamence's Hidden Power Flying, mixed Salamence’s Fire Blast, Choice Band Aerodactyl’s Double-Edge or Hidden Power Flying, Moltres’s and Charizard’s Fire Blasts, and even Zapdos’s Thunderbolt to forcibly chip each with Pursuit. If Dugtrio revenge kills Breloom, Mach Punch, followed up by Tyranitar's Pursuit, will KO it in return. Tyranitar also sets sand, which makes Breloom's Focus Punch damage stick against the sand-weak Fighting-resistant foes like Zapdos and Salamence. Despite Pursuit Tyranitar having the most synergy with Breloom, mixed and Dragon Dance Tyranitar might be better partners on hyper offense teams, as they have more offensive potential. If this choice is made, one should mitigate the Gengar weakness with Stun Spore or Hidden Power Ghost. Less popular Pursuit users like Metagross, Houndoom, and Umbreon are also potential Breloom partners, fitting well on teams without sand or those that prefer a different Tyranitar set.
Breloom sometimes struggles to get on the field due to its poor defenses, so it is commonly paired with pure or Substitute Baton Pass users like Zapdos, Celebi, and Vaporeon. Zapdos is the most common and consistent of the three, as it synergizes nicely with Breloom defensively and offensively: Zapdos can pass to Breloom to handle a Rock Slide from Tyranitar or to pressure Blissey and Snorlax that come in on Zapdos. Celebi can pass out of Pursuit Tyranitar into Breloom or catch Skarmory on the switch to deny Spikes with Breloom's Spore. Vaporeon is another Substitute + Baton Pass user that can create Substitutes that survive Blissey's Seismic Toss to pass to Breloom safely.
Breloom fits well on mixed offense teams. Mixed attackers lure in and weaken Skarmory, Celebi, and Zapdos for Breloom and vice versa, while Breloom compensates for their inability to break past the bulky core of Milotic and Blissey. These mixed attackers include mixed Salamence, offensive Swampert, Charizard, and mixed Zapdos. Using Charizard and Zapdos helps offensive teams check the tier's most fearsome physical threats without wasting a teamslot on a passive wall; both defensively cover Metagross, while Breloom covers physical Tyranitar. In general, offense teams need a strategy for checking Dragon Dance Tyranitar, and Mach Punch Breloom shores up that weakness without ceding momentum. Breloom is also great on offense teams that rely on trades to get into a favorable position. With partners that can take out just about any Pokemon one-on-one, like mixed or Choice Band Explosion Metagross, Self-Destruct Snorlax, and Endeavor Swampert, one can continuously trade KOs until there are few Pokemon left on either side; here, Spore, by disabling one of the key Pokemon remaining, can be devastating. Dugtrio can also perform trades via trapping and revenge killing; additionally, it can reverse trap opposing Dugtrio and enable Calm Mind sweepers, though one has to be careful about stacking weaknesses to Dragon Dance Salamence. Finally, Breloom fits very well on offense teams that feature setup sweepers like Dragon Dance Tyranitar; Calm Mind Jirachi, Suicune, and Celebi; or Substitute Aerodactyl, as sleeping a wall provides extra turns for them to set up and break through.
On stall and balance teams, Breloom is used to generate momentum and win the Spikes war, putting either the opposing Spiker or spinner to sleep. While both Skarmory and Forretress are appropriate Spikers, Forretress is the more common Breloom partner, as they both benefit from Pursuit Tyranitar. Forretress is also good at pressuring the Psychic-types that wall Breloom like Celebi, Claydol, and Starmie with Hidden Power Bug. As both Breloom and Forretress are weak to mixed attackers, they are often paired with a mixed wall like Blissey, Milotic, or specially defensive Zapdos; these are especially useful versus mixed Salamence, which is a very common Breloom answer. Aerodactyl is another good switch-in to mixed Salamence and acts very well as a late-game cleaner when used with Spikes. Additionally, Hidden Power Bug Aerodactyl can also mitigate Breloom’s weakness to Psychic-types, especially Celebi.