Gengar's combination of power and unpredictability make it a potent offensive threat. It has an excellent movepool backed up with great Speed and impressive Special Attack. Gengar's immunity to the popular Ground- and Fighting-type attacks (and Normal-type ones too) allows it plenty of opportunities to switch in and wreak havoc. Despite its immense power, Gengar does have its drawbacks. Its atrocious defensive stats means it will take massive damage from even neutral STAB attacks, while its weakness to Dark means it can be easily Pursuited by Tyranitar or Scizor if it isn't careful. However, its frailty shouldn't deter you from using Gengar—its wide range of powerful and disruptive moves make it a threat to even the best-prepared teams.
Since Gengar's excellent type coverage forces a lot of switches, it can use Substitute to great effect. It helps deal with Tyranitar and Scizor, two of Gengar's greatest nemeses, by scouting the switch and letting Gengar hit them with the appropriate 4x super effective attack. Substitute is especially important given the popularity of Choice Scarf Tyranitar, which would otherwise be able to pick off Gengar with near impunity. It also allows Gengar to evade status such as Celebi and Blissey's Thunder Wave. Shadow Ball and Focus Blast give Gengar the unresisted Ghost / Fighting coverage, while Hidden Power Fire in the last slot grants a quick OHKO on Scizor and Forretress while giving it a way of hurting specially defensive Skarmory reliably.Team Options & Additional Comments >>>
With the release of HeartGold and SoulSilver came a new toy for Gengar to play with: Pain Split. By utilizing a combination of Substitute and Pain Split, Gengar becomes nearly impossible to wall, even by Blissey. Pain Split also allows Gengar to safely run Substitute and Life Orb at the same time, all the while taking damage from sandstorm and hail; in fact, taking so much residual damage only increases the amount of HP that Gengar sucks away from its opponents. Gengar is also notorious for its ability to sweep, with its massive Special Attack stat and base 110 Speed. Although this set loses some super effective coverage due to the lack of attacking moveslots, Gengar still maintains perfect neutral coverage with the unresisted Fighting- and Ghost-type combination. A combination of base 130 Special Attack and high-powered moves ensures this Gengar is still a terrifying sweeper.
The combination of Substitute and Pain Split allows Gengar to take out Pokemon it normally would not be able to, most notably Blissey. After Substitute and two Pain Splits (or one if sandstorm is in effect), Blissey's health will low enough so that Focus Blast is a 2HKO. This means that Blissey will be forced to constantly heal herself or risk being KOed. Pain Split has 32 PP, while Wish and Softboiled have 16, meaning that Gengar can easily stall Blissey out. If Blissey does not use a healing move to conserve PP, then she is at huge risk of being 2HKOed by Focus Blast. Finally, most Blissey are unable to break Gengar's Substitutes, meaning it can usually come out of the duel unscathed.
Life Orb Gengar is a fearsome sweeper that has few true counters. With great Special Attack and Speed, great type coverage, as well as three immunities, Gengar is capable of dealing heavy damage to almost any team. Shadow Ball and Focus Blast give Gengar complete type coverage and hit some of the metagame's top threats for super effective damage. Focus Blast always OHKOes max HP Tyranitar in sandstorm, 2HKOes most Snorlax, and always OHKOes min HP Heatran. Thunderbolt offers a quick OHKO against Gyarados and 2HKOes max HP Suicune. In the last slot, Hidden Power Fire can be used for its additional power against most Steel-types (most notably Scizor and Forretress), but running Hidden Power Fire forces Gengar to have an imperfect Speed IV which means it will almost always lose the speed tie against opposing Gengar. Finally, Explosion allows Gengar to go out with a bang and possibly defeat Blissey.Team Options & Additional Comments >>>
Although it seems odd to use a Choice Scarf on something as fast as Gengar, its stellar type coverage allows Choice Scarf Gengar to act as an effective revenge killer for many of OU's most dangerous sweepers, including Dragonite, Gyarados, and Tyranitar.
Shadow Ball gives Gengar its requisite STAB attack and allows it to revenge threats such as Scarf Rotom-A, Azelf, and Starmie. Focus Blast is primarily useful for Tyranitar and Heatran, but can deal decent damage to Snorlax in a pinch. Thunderbolt turns Gengar into a great revenge killer for Dragon Dance Gyarados. Finally, Hidden Power Ice provides more reliability against Dragon Dance Dragonite, since Dragonite needs to be moderately weakened for Shadow Ball to KO. Gengar can also use Trick to cripple bulkier Pokemon such as Blissey and Snorlax, while Explosion allows it to revenge kill a large number of Pokemon with one move.Team Options & Additional Comments >>>
Gengar is a great and unexpected lead who can stop a large portion of the common leads in the metagame. For instance, Azelf and Aerodactyl must choose between setting up Stealth Rock or attacking Gengar since Icy Wind followed by Shadow Ball is a certain 2HKO on both. Additionally, Gengar can take out the opponent's lead almost all the time, sometimes even while keeping its Focus Sash intact.
Icy Wind and Shadow Ball are the bread and butter of this set. Icy Wind breaks the opposing lead's Focus Sash and lowers its Speed, allowing Gengar to outspeed and take it out with Shadow Ball on the next turn. Common suicide leads, such as Azelf, Aerodactyl, and Infernape, either get up their Stealth Rock or bring Gengar down to its Focus Sash. If they set up Stealth Rock, Gengar remains at full health with its Focus Sash still unactivated. However, if they attack, then Gengar succeeds at taking out the opposing lead and keeping Stealth Rock off of the field.
The rest of the moves enable Gengar to eliminate physical threats and leads who resist both Icy Wind and Shadow Ball. Counter is a great move for taking out common physical threats such as Machamp and Metagross, reflecting their attacks for double the damage. The last move should be Focus Blast, which allows Gengar to deal with Heatran and Tyranitar, two Pokemon who cannot be beaten otherwise. With a Mild nature, Gengar will 2HKO max HP Heatran with a Focus Blast followed by a Shadow Ball, while surviving with its own Focus Sash. Gengar also has a high chance of OHKOing max HP Tyranitar with Focus Blast with a Mild nature.Team Options & Additional Comments >>>
Protect allows Gengar to defeat most versions of the two Pokemon who give it the most difficulty in the Platinum metagame: Pursuit Tyranitar and Bullet Punch + Pursuit Scizor. After Gengar has switched in and Tyranitar or Scizor have then switched in as well, Gengar will first use Protect to see if Tyranitar or Scizor uses Pursuit. If either Pokemon uses Pursuit, Gengar will use the proper move to OHKO it. If neither Pokemon uses Pursuit, Gengar can safely switch out. Note that even with Protect, Gengar needs to remain wary of non-Choice Scizor with Bullet Punch and Pursuit and Choice Scarf Tyranitar with Pursuit. Shadow Ball and Focus Blast give Gengar perfect coverage, while Hidden Power Fire lets it OHKO Scizor that decide to Pursuit.Team Options & Additional Comments >>>
This mixed Substitute set allows Gengar to deal with many Pokemon who commonly switch into it, including Blissey, Scizor, and Snorlax. Substitute not only blocks status and eases prediction, but allows Gengar to Focus Punch without risk of being hit. Focus Punch 2HKOs Snorlax and even the most physically defensive Blissey after Stealth Rock, while OHKOing most Tyranitar. Even with split offensive EVs, Shadow Ball packs a hefty kick and is a reliable STAB. In the last slot, Hidden Power Fire lets Gengar dispatch Forretress and Scizor.Team Options & Additional Comments >>>
Sludge Bomb was left out of the main sets, as it offers rather poor type coverage despite being Gengar's most powerful attack. Most Grass-types, especially Celebi, won't enjoy a hit from Shadow Ball, and are unlikely to stay in on Gengar, as Gengar resists their main STAB. Gengar has Energy Ball and Giga Drain to hammer Swampert and Rhyperior, if either is a problem for your team. Psychic hurts Fighters more than Gengar's other attacks, but most of them won't enjoy boosted Shadow Balls, so it still remains a lesser option.
Mean Look can trap an opponent so Gengar can Explode on them and Perish Song can phaze opponents. Mismagius is better than Gengar in this respect due to Mismagius' higher Special Defense, but Gengar can employ Hypnosis (and it also has more Speed than Mismagius). Taunt can prevent Blissey from firing off Thunder Wave and Toxic, allowing you to switch in your physical attackers without fearing status. Will-O-Wisp can hit Tyranitar and Scizor hoping to switch in, but is usually better left to the Rotom Appliances. Destiny Bond works well in place of Explosion if you are sure that Gengar will be KOed with the following attack.
Because of Gengar's plethora of attacks, Expert Belt is a fine option. It allows Gengar to hit harder, but without the 10% recoil that Life Orb inflicts. If you're playing under Item Clause, you can use Black Sludge over Leftovers. Finally, Gengar can invest 72 EVs in Defense so that it always survives Choice Band Scizor's Bullet Punch assuming no prior damage.
Checks and Counters
Anything with Pursuit will ruin Gengar, especially Choice variants, although Weavile and Tyranitar fear Focus Blast, and Metagross won't enjoy a burn or repeated hits from Shadow Ball or Focus Blast, which can 2HKO with Choice Specs. 252/216+ Tyranitar always survives Timid Gengar's Life Orb Focus Blast. Choice Scarf Tyranitar deals a minimum of 78.2% to a non-switching Gengar with Pursuit, which can mean a guaranteed KO with a bit of residual damage. Spiritomb has both Pursuit and Sucker Punch and plenty of Special Defense to absorb Gengar's attacks. Scizor also makes an excellent counter as it can deal with Gengar whether it stays in or switches out with Bullet Punch and Pursuit respectively, but must beware of Hidden Power Fire.
Blissey does well against most sets; she can paralyze Gengar with Thunder Wave or wear it down with whichever special attack she happens to carry. Blissey can be easily shut down by Tricking a Choice item onto her or with the Substitute + Pain Split set, and must always beware of Explosion. Snorlax with Crunch does a fine job, especially Sleep Talk versions as they can absorb Hypnosis. Snorlax can also put the hurt on Gengar by packing Pursuit. Beware of Focus Punch, Focus Blast, and Explosion though. Jirachi and Bronzong both do well with their high Special Defense and neutrality to most of Gengar's attacks. Heatran, especially Choice Scarf ones, can switch into everything barring a Fighting-type attack, and gets a boost from Hidden Power Fire. Even without a boost, Fire Blast will OHKO standard Gengar 100% of the time when accounting for Stealth Rock damage.
Gengar's attacking power and incredible movepool mean that countering it is a rather daunting prospect. Thankfully, Gengar is incredibly fragile and most neutral attacks will at least score a 2HKO.