Dusknoir @ Leftovers
Trait: Pressure
EVs: 252 HP / 252 Atk / 4 Spe
Adamant Nature (+Atk, -SpA)
- Substitute
- Focus Punch
- Shadow Sneak
- Will-o-Wisp
Dusknoir is extremely underrated in OU. Yes, I know his defensive sets are outclassed by jellicent and cofagrigus, but the SubPunch set is actually very useful. Thanks to its good defenses (45/135/135), Dusk can easily set up a Substitute and fire off strong Focus Punches, dealing a large amount of damage to many things that don't resist it.
252+ Atk Dusknoir Focus Punch vs. 252 HP / 88+ Def Ferrothorn: 202-238 (57.38 - 67.61%) -- guaranteed 2HKO
252+ Atk Dusknoir Focus Punch vs. 248 HP / 0 Def Scizor: 150-177 (43.73 - 51.6%) -- 99.61% chance to 2HKO after Stealth Rock
252+ Atk Dusknoir Focus Punch vs. 252 HP / 0 Def Politoed: 190-224 (49.47 - 58.33%) -- guaranteed 2HKO after Stealth Rock
252+ Atk Dusknoir Focus Punch vs. 4 HP / 0 Def Breloom: 180-212 (68.7 - 80.91%) -- guaranteed 2HKO after Stealth Rock (and puts it in Shadow Sneak's ko range)
252+ Atk Dusknoir Focus Punch vs. 4 HP / 0 Def Terrakion: 328-386 (101.23 - 119.13%) -- guaranteed OHKO
252+ Atk Dusknoir Shadow Sneak vs. 0 HP / 0 Def Starmie: 138-164 (52.87 - 62.83%) -- guaranteed 2HKO (plus it can take one Hydro Pump)
252+ Atk Dusknoir Shadow Sneak vs. 4 HP / 0 Def Gengar: 182-216 (69.46 - 82.44%) -- guaranteed 2HKO
252+ Atk Dusknoir Shadow Sneak vs. 252 HP / 36 Def Jellicent: 152-182 (37.62 - 45.04%) -- guaranteed 3HKO (2hko with a bit of prior damage)
252+ Atk Dusknoir Focus Punch vs. 56 HP / 0- Def Kyurem-B: 332-392 (81.97 - 96.79%) -- guaranteed OHKO after Stealth Rock
As you can see, Dusknoir's 100 base attack is not to be taken lightly. Against physical attackers Dusknoir can't do much to, it still has one last trick up its sleeve, and that is Will-o-Wisp. It cripples things like Conkeldurr (which used to be a perfect counter to Dusk, but now that the Sheer Force set is common, it's rendered useless and Ice Punch won't break its sub).
Also, Dusknoir is a ghost-type, meaning it can spinblock while firing off Focus Punches, and that's why it works so well when aided by Spikes and Stealth Rock. It's still bulky:
252 Atk Terrakion Stone Edge vs. 252 HP / 0 Def Dusknoir: 127-150 (43.19 - 51.02%) -- guaranteed 3HKO
252+ Atk Choice Band Technician Scizor Bullet Punch vs. 252 HP / 0 Def Dusknoir: 126-148 (42.85 - 50.34%) -- guaranteed 3HKO
252 SpA Keldeo Hydro Pump vs. 252 HP / 8 SpD Dusknoir in rain: 225-265 (76.53 - 90.13%) -- guaranteed 2HKO
+1 252 Atk Salamence Outrage vs. 252 HP / 0 Def Dusknoir: 234-276 (79.59 - 93.87%) -- guaranteed 2HKO
252+ Atk Choice Band Metagross Meteor Mash vs. 252 HP / 0 Def Dusknoir: 213-252 (72.44 - 85.71%) -- guaranteed 2HKO
It can live those attacks and either burn them or sometimes even setting up a sub.
So yeah. Don't use its defensive set which is made of fail and is completely outclassed, use this set.