Threats (Offensive and defensive)
Charizard @ Charizardite Y
Ability: Blaze
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
- Blast Burn / Fire Blast
- Air Slash
- Solar Beam
- Dragon Pulse
Mega Charizard Y is a very threatening Pokemon in 1 vs 1 as it has as good as perfect coverage and without the necessity of running Roost can now go for a pretty all-offensive movepool that will eviscerate a lot of things. Because it gets Sun on the turn it mega evolves, the necessity to run Focus Blast greatly drops, as it can just spam Solar Beam without having to worry about the weather, making the only pure counter Heatran, or in some cases the Lati@s, who will not be KOd by Dragon Pulse.
As for damage, most Pokemon are completely destroyed by a STAB Blast Burn in Sun. Fire Blast can also be an option for if you are trying to play safe, but damage is pretty much the most important factor in 1 vs 1
Notable Checks and counters
- Latios
- Latias
- Heatran
- Tyranitar
- Thundurus-I
- Dragonite
- Kyurem-B (Scarfed)
Charizard @ Charizardite X
Ability: Blaze
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Flare Blitz
- Outrage
- Dragon Dance
- Will-O-Wisp / Earthquake
Deadly in OU, deadly in 1v1. Hits ridiculously hard. Base 130 Attack, Dragon Dance, Tough Claws, STAB Flare Blitz, Dragon Claw/Outrage. Some variants also run Will-O-Wisp to get around Aegislash better, as well as Azumarill.
Notable checks and counters
- Landorus-I with Rock Slide and E-power
- Landorus-Therian
- Azumarill
- Hippowdon
- Quagsire
- Scarfchomp
- Latios
- Latias
- Tyranitar
Mawile @ Mawilite
Ability: Intimidate
EVs: 252 HP / 252 Atk / 4 Spe
Adamant Nature
- Play Rough
- Iron Head
- Sucker Punch
- Swords Dance
Mega Mawile is quite threatening if not one of the most threatening Pokemon you can and will ever face in 1 v 1. This Swords Dance set just amplifies the difficulty for certain Pokemon to still check it when they waste a single turn. Pretty straightforward set that is very similar to one of the ones used it used to run in OU
Notable checks and counters
- Heatran
- Charizard-X (WoW variants)
- Landorus-Therian
- Charizard-Y (till an extent)
Kyurem-Black @ Choice Scarf
Ability: Teravolt
EVs: 252 Atk / 4 SpA / 252 Spe
Naughty Nature
- Outrage
- Fusion Bolt
- Iron Head
- Ice Beam
Choice Scarf, outspeeds a large amount of the tier, OHKOs a large amount with Outrage. Coverage in Fusion Bolt, Iron Head and that's about all it needs.
Notable checks and counters
- Scarf Latios
- Scarfed Pokemon with a strong stab supereffective move
Greninja @ Choice Specs
Ability: Protean
EVs: 4 HP / 252 SpA / 252 Spd
Timid Nature
- Hydro Cannon / Hydro Pump
- Ice Beam
- Dark Pulse
- Hyper Beam / Extrasensory
Notable checks and counters
Its flexibility make it near impossible to call a Pokemon a check or a counter. However, powerful scarfed Pokemon can usually pull through
Gyarados @ Gyaradosite
Ability: Intimidate
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
- Dragon Dance
- Waterfall
- Earthquake
- Outrage
Gyarados Mega seems more love in 1 vs 1 as its natural bulk and great offensive presence enable it to easily kill at least one Pokemon, something it can also usually do in OU. This Dragon Dance set is exclusive to 1 vs 1 and enables it to deal with common counters such as Kyurem-B, thus allowing it to defeat them 1 on 1. Also helps it break past most dragon types that would otherwise wall this set.
Notable checks and counters
- Azumarill
- Whimsicott
- Mega Gardevoir
Dragonite @ Choice Band
Ability: Multiscale
EVs: 252 Atk / 24 Def / 232 Spe
Adamant Nature
- Outrage
- Earthquake
- Extreme Speed
- Fire Punch
For those of us familiar with OU, I am pretty sure I can confidently say that Choice Band Dragonite is one of the most powerful wallbreakers that does a divine amount of damage. As good as everything will be KOd when hit by one of its devastating blows, not to forget its dreadful Outrage. As far tanking hits goes, bc of Multiscale, it will survive a lot of Ice attacks as well as fairy type attacks. The 24 EVs in defense insure that you live everything up to a Choice Banded Azumarill's Play rough with Multiscale intact and 2HKO it back with Earthquake.
The weakness policy is most definitely an option as well, however at the cost of speed
Notable checks and counters
- Kyurem-B
- Greninja
- Clefable
Slaking @ Choice Band
Ability: Truant
EVs: 252 Spd / 252 Atk / 4 HP
Adamant Nature
- Giga Impact
- Earthquake
- Hammer Arm
- Night Slash
Due to the 1 turn nature of 1v1 battles, Slaking's ability Truant no longer becomes something of major consequence. Band + Giga Impact essentially destroys everything that doesn't resist.
Notable checks and counters
- Anything with Protect
- Aggron (Mega) and metal burst Aggron
- Things that can tank Band EQ and kill in 2 turns
- , most things with Sturdy
Azumarill @ Choice Band
Ability: Huge Power
EVs: 88 HP / 252 Atk / 4 Def / 164 Spe
Adamant Nature
- Aqua Jet
- Play Rough
- Knock Off / Superpower / Ice Punch
- Waterfall
Band sets generally. Survives standard Scarf Kyurem-B Fusion Bolt, OHKOs back, survives Latios,OHKOs back etc. Non-band sets (AV) also get around big threats such as Mega Charizard - Y.
Notable Checks and counters
- Aegislash (non-knock off variants)
- Mega Venusaur
- Band Kyurem-B
- Mega-Mawile
Sawk @ Choice Band
Ability: Mold Breaker
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Close Combat
- Knock Off
- Ice Punch
- Earthquake
Sturdy Variants with Band manage to beat things like Metal Burst Aggron and Latios. Mold Breaker also breaks through any Sturdy Pokemon that might be trying the FEAR Strategy
Notable Checks and counters
- Kyurem-B (Scarfed)
- Azumarill
Aegislash (plethora of effective sets)
High bulk, high attack, unresisted coverage. Air Balloon or Lefties as popular items (Air Balloon prevents EQ and often forces a contact move, causing the -2 drop with King's Shield).
Notable checks and Counters
- Charizard Y
- Charizard X
- Heatran
Other counters differ depending on what it is running
Whimsicott @ Leftovers
Ability: Prankster
EVs: 248 HP / 236 Def / 24 Spe
Bold Nature
- Leech Seed
-Taunt
- Protect
- Substitute
Annoying as hell. Leech Seed + Sub stalls out a large amount of the tier, makes people RQ all day.
Notable checks and counters
- Mega Venusaur
- Most Fire types
- Mega Gardevoir
Aggron
Metal Burst + Sturdy.
Notable checks and counters
- Sturdy and or Mold Breaker / Teravolt / Turboblaze
- Whimsicott
- Fake Out + Fighting type
- Other Sturdy users
Note: A lot of these sets should only be used in 1 vs 1, as they are less effective in OU
Special shout out to Sempi for helping me write this + this aiding source