Voodoom's greatest asset is its base 110 Speed, which allows it to Speed tie with Latios, Latias, Kitsunoh, and Mega Metagross, all of which Voodoom threatens with its Dark-type STAB moves. Additionally, Voodoom's two abilities, Lightningrod and Volt Absorb, along with a quadruple resistance to Dark and an immunity to Psychic, give Voodoom some opportunities to switch in. Voodoom has decent Special Attack and a STAB combination that is only resisted by Fairy-types, and in conjunction with Voodoom's good Speed, it has a niche as a fast special cleaner.
Unfortunately, Voodoom's STAB combination and movepool leave it completely walled by Fairy-types, and its low Attack and just passable Special Attack leave it reliant on Life Orb for any meaningful damage output. Voodoom's relative frailty leaves it taking significant damage from every offensive Pokemon in the tier and makes it susceptible to revenge killing from fast attackers, Choice Scarf uses, and all forms of priority bar Sucker Punch. Lastly, Voodoom faces major competition from every other fast Dark- and Fighting-type Pokemon in the tier, especially Weavile and Keldeo, and requires significant team support to function well.
Dark Pulse is Voodoom's most spammable move, as it hits neutral targets for decent damage. It also allows Voodoom to revenge kill Ghost- and Psychic-types. Close Combat hits Assault Vest Colossoil, Chansey, and specially defensive Heatran hard, 2HKOing all three. Aura Sphere can be used to provide Voodoom with a more powerful STAB option and hit Ferrothorn harder, but it is unable to 2HKO Chansey or Assault Vest Colossoil. Psychic is needed to hit Fighting-types super effectively and allows Voodoom to 2HKO all variants of Keldeo and Tomohawk, as well as hit Poison-types such as Plasmanta, Mollux, and Mega Venusaur hard. In the last moveslot, Taunt is preferred to prevent entry hazards, boosting moves, and Defog from being used. Taunt also helps wear down defensive Pokemon by denying them access to recovery or status removal. If stopping status moves is not a concern, Vacuum Wave can be use to give Voodoom access to a STAB priority move, allowing it to check faster threats such as Stratagem and Mega Lopunny.
Life Orb is needed to offset Voodoom's lackluster base Special Attack stat and guarantee the OHKO or 2HKO on several Pokemon. For example, Colossoil is only 2HKOed by an unboosted Close Combat, while a Life Orb-boosted one has a good chance to OHKO it, and Voodoom can't OHKO Latios or Latias without Life Orb. Lightningrod is the preferred ability, as the potential boost to Voodoom's Special Attack significantly increases its damage output. Volt Absorb can be used to help offset entry hazard damage and Life Orb recoil, but Voodoom appreciates the increase to its damage output more. The chosen EV spread gives Voodoom as much Special Attack and Speed as possible. A Speed-boosting nature is chosen to allow Voodoom to outspeed Keldeo and Speed tie with base 110 Speed Pokemon, such as Mega Metagross, Kitsunoh, Latios, and Latias. A Hasty nature is preferred, as it allows Voodoom to switch into Electric-, Ghost-, and Psychic-types more easily due to them primarily being special attackers, although Naive is an option to better deal with Colossoil and take priority attacks, particularly Sucker Punch, Bullet Punch, and Aqua Jet, better.
Dark Pulse is Voodoom's most spammable move and should be used as such. If the opponent has a Fairy-type on their team, you can expect them to switch to it. Predicting the switch and sending in your own Fairy-type check, such as Mega Scizor, can allow your team to grab momentum. Try to bait Electric-type moves through Pokemon weak to Electric, such as Gyarados, and then switch to Voodoom to activate its ability. Voodoom can also make for a decent anti-lead due to its access to a fast Taunt and ability to punish Volt Switch users.
Any Pokemon that can reliably check Fairy-types make for great teammates. Fire-types such as Heatran, Pyroak, and Talonflame are notable checks to Clefable, Sylveon, and Mega Altaria. Steel-types such as Scizor, Ferrothorn, Skarmory, and Mega Metagross help check Fairies as well. Scizor, Ferrothorn, and Skarmory are also capable Mega Diancie checks and can provide Defog or entry hazard support. Cyclohm, Rotom-W, Thundurus, and other Electric-types can check Talonflame. Rock-types such as Stratagem and Tyranitar also check Talonflame. Fairy-types themselves can handle the Fighting-types that Voodoom attracts. Specially attacking Fairy-types, such as Mega Diancie and Togekiss, appreciate Voodoom's ability to check Chansey. Sylveon and Clefable can also keep Voodoom healthy with Wish and Heal Bell support. Pokemon that are weak to Electric-type attacks, such as Gyarados and Talonflame, can draw in Electric-types that Voodoom can capitalize on.
Thunder Wave can be used to cripple switch-ins, but it is usually ineffective against Voodoom's most common switch-ins, Fairy-types; Sylveon, Clefable, and Mega Altaria have ways to remove status ailments and Azumarill is slow to begin with. However, it can help against some variants of Mega Altaria and can be bounced back by Mega Diancie for a Special Attack boost or some recovery. Earthquake can be used to OHKO offensive variants of Mollux and Heatran as well as bulkier sets with minor Attack investment and some prior damage. Knock Off can be used to remove the items of opposing Pokemon, such as Choice Scarf users, Chansey, and Colossoil. Baton Pass can be used to help gather momentum; Voodoom attracts Fairy-types to no end, so using Baton Pass on a predicted switch can put the foe in a disadvantageous position. Memento is an option to help a teammate get in good position for a sweep. Substitute and Pain Split can make use of Voodoom's high Speed to help wear down walls and to protect Voodoom from status conditions. Unfortunately, Substitute can not protect Voodoom from Pixilate Hyper Voice from the likes of Mega Altaria, Mega Gardevoir, and Sylveon.
Checks and Counters
Fairy-types: Every common Fairy-type can tank a hit from Voodoom and OHKO it with its STAB moves. Only Mega Gardevoir and Mega Diancie have anything to fear from Voodoom's attacks, and Sylveon, Clefable, and Mega Altaria can switch into Voodoom effortlessly.
Priority Users: Priority users such as Scizor, Talonflame, Technician Stratagem, Conkeldurr, Breloom, and Azumarill can deal major damage to Voodoom with their priority attacks before it gets a chance to move.
Faster Pokemon: Faster Pokemon such as Tornadus-T and Mega Lopunny can outspeed Voodoom and hit it hard with their STAB moves. Choice Scarf users such as Volkraken and Keldeo can also outspeed and KO Voodoom.
Bulky Attackers: Due to the middling power of Voodoom's attacks and its relative frailty, anything that can take a hit and retaliate can feasibly check Voodoom. Scizor, Volkraken and both Mega Charizard formes can take a hit and OHKO or heavily damage Voodoom, and even Fighting-types, such as Keldeo and Revenankh, can take a Psychic and OHKO Voodoom.