There's so much more to Gengar's malevolent exterior—in fact, Gengar is even more terrifying in practice than its appearance. Gengar still makes a potent offensive threat in the fifth generation thanks to its power, unpredictability, and excellent offensive movepool. Its set of immunities help it switch into common moves with impunity, giving it ample opportunities to come in and wreak havoc. Despite Gengar's positive traits as a sweeper, it does have two notable drawbacks: its paper-thin defensive stats, which make it take massive damage even from neutral attacks, and its weakness to Dark-type moves, which leaves it vulnerable to Pursuit if it isn't hiding behind a Substitute. However, the newly added Team Preview does allow for the scouting of possible Pursuit users, making the latter drawback less threatening. Don't let Gengar's atrocious defensive stats discourage you though; its offensive potency can definitely disrupt unprepared teams.
This is one of Gengar's deadliest sets to use with the proper timing. With Disable being upgraded to perfect accuracy in Black and White, Gengar can take advantage of this to great effect with its useful immunities combined with Substitute. The simple premise of this set is to hide behind a Substitute to overcome Pursuit users, avoid paralysis, and to make Disable easier to pull off. Common walls such as Ferrothorn and Blissey, who rely on one attacking move to deal with Gengar, find themselves in a very tight position after their move has been Disabled. Even sweepers that use two coverage moves find themselves in very tight situations; prime examples include Substitute Landorus, Conkeldurr without Stone Edge, and Gliscor. Gengar's great neutral coverage lets it batter many Pokemon for high damage, making it difficult to wall.Team Options & Additional Comments >>>
The Pain Split set is akin to the Disable set, but the approach to this set is much more offensive. Pain Split acts like a third attacking move capable of muscling through typical counters with massive HP stats such as Blissey, Chansey, and Snorlax. Furthermore, Pain Split works perfectly in conjunction with Substitute and Life Orb, and even benefits from the residual damage from sandstorm and hail. The closer Gengar's health bar gets to zero, the more HP Gengar can suck away from its opponents. Gengar's coverage is impressive, and it can act as a fail-safe sweeper at any given time even with the absence of an extra coverage move.
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 be low enough that Focus Blast 2HKOes. 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. Finally, most Blissey are unable to break Gengar's Substitutes, meaning Gengar can usually come out of the duel unscathed.Team Options & Additional Comments >>>
By giving up a status move, Gengar can obtain better super effective coverage than the tried and true Shadow Ball + Focus Blast. The choice between Substitute and Protect is heavily influenced by the needs of Gengar's team, but each option has its own advantages. The primary difference between Substitute and Protect is that Substitute Gengar is a setup variant that takes advantage of an opponent being forced to switch, while Protect Gengar can scout against Pokemon that are already in front of it. Substitute gives Gengar free turns to attack behind the safety of its Substitute, but leaves it very open to priority and faster Pokemon if the Substitute is not up; additionally, the Substitute can be broken via Volt Switch, which can leave Gengar completely open next turn against trappers and faster Pokemon. Protect gives Gengar immediate safety and lets it safely check the moves of Choice-locked switch-ins, easing prediction, but it will always be a glass cannon.
A key factor in choosing between Protect and Substitute is longevity. Substitute Gengar's lifespan can be short with Stealth Rock, passive effects, and the cost of each Substitute eating away at it. Protect Gengar does not need to rip away 25% of its HP just to keep safe, but this is high risk high reward; Protect ensures Gengar sticks around for as long as you need it, as you almost always know what your opposition is planning no matter how fast they are and you can make the correct choice next turn, but due to Gengar's fragile defenses, if you do make a mistake such as leaving it in against a Pokemon that was bluffing a Choice item or scouting a Pokemon's move only to have it set up on the Protect, Gengar will likely pay with its life. As for the attacking options, Shadow Ball and Focus Blast's unrivaled coverage might go without saying, but Hidden Power Fire gives Gengar added super effective coverage, allowing it to OHKO Scizor, Breloom, and Ferrothorn while dealing hefty chunks to Jirachi and Bronzong as well as letting Gengar take on Skarmory without risking a Focus Blast miss. Life Orb is preferred for the power increase that makes Gengar hard to switch in on. Black Sludge trades power for extended longevity, allowing Gengar to survive in Sandstorm and against the constant entry hazard damage it takes from switching, making it nearly ideal for Substitute variants if you can stand the attack power loss.Team Options & Additional Comments >>>
With such a diverse movepool, Gengar can easily catch any of its counters off-guard with the appropriate move. Gengar has access to both Hypnosis and Will-O-Wisp; the former can sleep a counter and effectively remove it from the battle, while the latter can be used to spread burn status on physical counters, particularly Tyranitar, Scizor and Jirachi. Gengar can also get around Blissey, its best counter, with a combination of Mean Look, Perish Song and Hypnosis. It can also use Taunt to prevent Blissey from healing. It's important to note the aforementioned moves' shaky accuracy, and that one miss or misprediction can be fatal due to Gengar's atrocious defensive stats. Gengar is therefore better off firing attacks than spreading status around.
Gengar can also pull off a myriad of other sets. The most effective set not listed here would have to be a Choice Scarf set, a great revenge killer. However, its weakness to Pursuit costs it a lot of usage. Gengar can also use Substitute and Focus Punch to take care of dedicated special walls like Blissey and Heatran if your team is in need of a great lure. You can combine Counter and Focus Sash for a real surprising but effective set. Thanks to Gengar's terrible defenses, pretty much any attack will OHKO you, allowing you to do huge amounts of damage back with Counter. If you want to get really fancy, use Destiny Bond on the same set to get a bonus KO. Gengar's physical movepool is actually really good, unfortunately its Attack stat is not, so a completely physical set is not advised.
In addition to the moves listed on the sets, Gengar has quite a few great attacking options to spare. Thunderbolt is a great attack in general and helps you counter Skarmory. Thunder is an option if you're using a rain team, since Gengar does have a resistance to Grass. Hidden Power Ice can be used on any set to check Dragonite, Landorus and Salamence. Hidden Power Fire serves as a great lure to the omnipresent Scizor and Ferrothorn. Sludge Bomb hits Grass-types harder but that's about it. Energy Ball and Giga Drain are 100% accurate deterrents to Politoed and Tyranitar, but neither come close to OHKOing them. Grass-type moves would also help you get around Gastrodon who does surprisingly well against Gengar. Explosion got nerfed in the fifth generation but it can still catch Blissey by surprise. If your team is loaded with status inflictors such as Toxic Spikes, both Hex and Venoshock suddenly become viable attacks. Dark Pulse isn't a bad attack but Shadow Ball gets STAB and better neutral coverage. Clear Smog and Perish Song aren't great but they're Gengar's only phazing options. Gengar can use its 3 immunities and many resistances to set up Trick Room, but there are better options for this since it is both fast and frail. Finally, Grudge can be an interesting way to mess with things like Terrakion by draining all of its Stone Edges, but moves like Destiny Bond and Disable are better for this.
Checks and Counters
Gengar is one of the few Pokemon with both a great movepool and the stats to use it, which is why it's been OU since the first generation. With that said, there are still a good number of ways to get around Gengar should you encounter one. The easiest way is to use strong priority. Scizor's Bullet Punch is a clean OHKO on Gengar. Any Sucker Punch user can also score a clean OHKO against Gengar, although you must watch out for Substitute and Will-O-Wisp. Even strong neutral priority like Mamoswine's Ice Shard or Azumarill's Aqua Jet does enough to force Gengar out or kill it straight up. The second best way to attack a Gengar is with a strong user of Pursuit. Scizor, Metagross, and Tyranitar can take Gengar's attacks and OHKO with Pursuit even if Gengar doesn't switch. Weavile and Heracross aren't seen much in OU but they can also checkmate Gengar with Pursuit.
Gengar's defenses are so poor that any attack it doesn't resist will 3HKO it at worst. For example, Landorus can survive a Shadow Ball and KO with Stone Edge. Blissey's Ice Beam or Flamethrower can 3HKO Gengar, but it must watch out for sets like Pain Split, Disable, and Destiny Bond. Pokemon like Celebi and Jirachi can survive its attacks and OHKO with Psychic. Conkeldurr usually has max HP to score an OHKO with Payback, and it can also mess with Disable sets by using Mach Punch. Tentacruel only cares about Thunderbolt, but it can use Scald and shrug off Shadow Ball with its high Special Defense. That is the general formula for directly countering Gengar, decent Special Defense and a solid neutral or super effective hit. Bulky Water-types like Politoed, Vaporeon, and the aforementioned Tentacruel fit this bill.
Checking Gengar is much easier than directly countering it. Almost every Choice Scarf user in OU has a move that will outspeed and OHKO Gengar. This includes, but is not limited to: Politoed, Latios, Terrakion, Tyranitar, Rotom-W, Heatran, Haxorus, and Infernape. Pokemon that are naturally faster than Gengar can also do a great job, such as Starmie, Tornadus, Azelf, and Jolteon. Of course, all of these Pokemon have incredible difficulty finding a chance to switch in. Gyarados, Salamence, and Dragonite can set up a Dragon Dance or two on Gengar if they've invested in HP. Volcarona can set up Quiver Dances if Stealth Rock is not up.