Moves
Air Slash is the most obvious choice of move for Togekiss, as it's a decently strong STAB move that, with Serene Grace, has a 60% flinch chance. This allows it to hit the majority of the metagame for decent damage, notably, Mega Gyarados. Thunder Wave allows Togekiss to essentially double its Speed, outrunning fully invested Deoxys-S, while adding the chance for full paralysis on top of the flinch chance from Air Slash. Z-Thunder Wave raises Togekiss's Special Defense by one stage, allowing it to survive hits from Pokemon such as Choice Specs Greninja, Choice Scarf Porygon-Z, and uninvested Mega Gardevoir. Roost allows Togekiss to create an HP buffer that allows it to survive attacks if the opponent is able to move, allowing the user to mitigate risk by a significant amount in many matchups, such as against uninvested Mega Gardevoir and uninvested Tapu Lele, and the removal of its Flying typing allows Togekiss to take neutral damage from attacks like Stone Edge from Golem, Bolt Strike from Victini, and Ice Beam from Choice Specs Greninja. Nasty Plot allows Togekiss to break through walls such as Mega Slowbro, Umbreon, Kyurem, and Deoxys-S. Alternatively, Charm lets it beat Groundium Z Golem, Donphan, physical Dragonite, and Mega Gyarados more reliably. Encore can force opposing Pokemon to continue using setup moves, allowing Togekiss to slowly chip away at their HP with safety. This lets it lock Pokemon such as Mega Gardevoir, Mega Charizard X, and Zygarde into moves such as Calm Mind, Dragon Dance, and Substitute, respectively, as well as beating stall Pokemon like Mega Slowbro and Stored Power Necrozma. Substitute can be combined with Air Slash and Thunder Wave to further protect Togekiss from being attacked. This can help against uninvested Tapu Lele and Mega Gardevoir.
Set Details
208 HP EVs and 72 Special Defense EVs with a Calm nature allow Togekiss to survive many strong hits from uninvested Tapu Lele, uninvested Mega Gardevoir, and Choice Specs Greninja, giving it the opportunity to use Z-Thunder Wave. The HP EVs also allow Togekiss to deal with physical attackers like Mega Gyarados with ease. Landing Air Slash on a paralyzed Pokemon gives the foe a 30% chance to move each turn. This allows Togekiss to take many opponents entirely through flinches without needing Roost or Nasty Plot. Electrium Z allows Togekiss to use Z-Thunder Wave to boost its Special Defense by one stage. This helps against Choice Scarf Porygon-Z, Choice Specs Greninja, uninvested Tapu Lele, and uninvested Mega Gardevoir. 228 Speed EVs allow Togekiss to outspeed maximum Speed Deoxys-S after Thunder Wave. Serene Grace boosts the chance of Air Slash flinching to 60%, which helps against Tapu Lele, Mega Gardevoir, Tapu Fini, and Primarina.
Usage Tips
Keep in mind that the foe has a 70% chance to not attack each turn if Air Slash lands. Substitute can be used against Pokemon that tend to use moves like Calm Mind, such as Magearna, Tapu Lele, and Mega Gardevoir, as it can create a barrier that allows Togekiss to survive a powerful attack in case it doesn't land a flinch. Against Magearna specifically, use Z-Thunder Wave turn 1, then use Substitute, then spam Air Slash. Use Substitute again when it breaks Togekiss's Substitute, as Togekiss can survive a +2 Fleur Cannon after a Roost at +1 Special Defense, then use Substitute again. Make sure you have a Substitute up at almost all times, to prevent the opposing Magearna from using Pain Split. Use Togekiss if your opponent doesn't have any Pokemon that win via being faster like Smeargle, Vivillon, or Jumpluff.
Team Options
Pokemon that can efficiently dispatch Steel-, Electric-, and Rock-types like Rockium Z Golem, Zeraora, and Magnezone are helpful as teammates for Togekiss, such as Golem, Donphan, and Garchomp. In return, Togekiss can beat Water- and Grass-types like Primarina and Mega Venusaur for them. Pokemon such as Kyurem and Dragonite that benefit from Togekiss dispatching uninvested Mega Gardevoir, Mega Gyarados, and Greninja are good teammates, especially if they match up well versus the Steel-, Electric-, and Rock-types that hold Togekiss back such as Golem, Zeraora, and Celesteela. Pokemon that can deal with Toxic stallers like Blissey and Chansey, such as Ferrothorn, are good teammates for Togekiss, as are teammates that can deal with fast Poison-types like Naganadel and Substitute Mega Gengar, such as specially defensive Flame Charge Mega Charizard X.