With its base 125 Attack and 120 Base Power STAB move, Heracross is one of the most feared Pokemon in the game. Heracross is in fact so dangerous that many of its counters can lose to it. Weezing and Dusclops dare not burn it thanks to Guts, while users of Dugtrio risk being potentially swept by Endure + Salac Berry Heracross variants.
Choice Band Heracross can deal good damage to any Pokemon in the game. It has a hard time staying alive for long, but it packs a great, great punch. If Heracross switches into the likes of Blissey's Thunder Wave, its Focus Punch will OHKO Skarmory, while a powered-up Facade does about 70% to Weezing. Hidden Power Ghost is mostly to take down Gengar and Dusclops, but Megahorn will usually do more than enough damage to them. Sleep Talk allows Heracross to switch into a sleep-inflicting move, such as Spore, and surprise the opponent with a Guts-boosted attack. Keep in mind that Sleep Talk will not select Focus Punch, however.
The EV spread—maximum Attack and Speed—is straightforward; the choice of nature is less so. An Adamant nature maximizes Heracross's damage output, but a Jolly one lets Heracross beat out the multitude of Pokemon that aim to outrun the more standard Adamant Heracross.
While Megahorn is obvious, powerful STAB and one of Heracross's main selling points, both Rock Slide and Brick Break are viable coverage options. Rock Slide is the more useful move as it dents threats such as Salamence, Gyarados, and Gengar. However, Heracross that run both Rock Slide and Megahorn lack a nice 100% accuracy move to reliably kill a weakened foe. STAB Brick Break is a great solution to this dilemma, but leaves Heracross walled by Flying-types. Its attacks hit hard during sleep as Guts is activated, which gives it essentially a Choice Band boost. Although it requires a bit of luck to be effective, it makes for a great sleep absorber.
A ton of HP investment ramps up Heracross's bulk, some Speed EVs let it hit a stat of 244, and its damage output is fully maximized.
Heracross is an awesome sweeper. With boosts from both Guts and Swords Dance, Heracross will sweep the hell out of Weezing and anyone else. Focus Punch is for a predicted switch to Skarmory, and after a Swords Dance, Megahorn does enough to everything to make Brick Break useless. Jolly variants can elect to run less Speed investment and raise HP instead.
This is a ticket to an easy sweep if your opponent lacks priority or Tyranitar. After one Swords Dance and a Swarm boost, this can OHKO Gengar, Skarmory, Suicune, and many others thanks to its insane Attack and the incredible Base Power of Reversal.
A Speed stat of 264 lets Heracross beat all base 130 Speed foes after a Salac boost, but you'll usually just want to run maximum Speed investment as this will help against random Pokemon with Agility or a Salac boost of their own.
Make sure Skarmory is out of the way, set up, and sweep their team. With a 30 HP IV, Salac Berry activates after the third Substitute, so don't be afraid to use this in sandstorm.
Heracross's movepool has everything it needs for it to be an extremely potent threat in ADV OU—a 120 Base Power STAB move, which, along with its other STAB and Rock Slide, provides nearly flawless coverage, hitting everything at least neutrally apart from the irrelevant Nidoking and Nidoqueen. It has access to Focus Punch, which allows it to muscle past one of its prime counters—Skarmory—and an excellent boosting move in Swords Dance. However, unlike the likes of Salamence and Tyranitar, which have all they need and more in the movepool department, Heracross lacks an expansive pool of viable moves.
A Bulk Up set is an interesting prospect for Heracross, with either 3 attacks, or Rest and Sleep Talk alongside Megahorn. However, the former variant is outclassed by its Swords Dancing counterpart, as many of its counters OHKO it even at +1 Defense, making the defensive boost rather irrelevant, and Heracross is much more destructive with Swords Dance. The latter set is severely walled by Salamence and Gyarados. Both Bulk Up sets are also incredibly handy Spikes fodder for Skarmory, so Magneton is an advised teammate for Bulk Up Heracross. Earthquake can potentially do that little bit of extra damage to finish off Metagross and Jirachi from a slightly higher range of health, and could be potentially fit in as a fourth option on the Choice Band set, but otherwise, it is difficult to fit Earthquake onto Heracross. Toxic is always an option, but in Heracross's case, it is rather pointless, as Heracross is much better off repeatedly bashing at its counters than trying to wear them down with status, due to its immense attacking power.
Counter is a potential option, although many of Heracross's best counters OHKO it with Flying STAB, such as Skarmory, enemy Heracross, and Gyarados. Counter is difficult to use on Heracross, as it resists three of the most common physical attacking types—Fighting, Ground, and Bug—so few players will aim attacks of those types at Heracross. Heracross is often better off simply attacking users with Normal- and Rock-type attacks, and Poison- and Ghost-type moves are extremely rare. Heracross could potentially Counter on a Weezing Sludge Bomb, or a Dusclops Shadow Ball. Hidden Power Flying is a highly niche option that can be used specifically to cover other Heracross. Similarly to Earthquake, it will most likely see use in the fourth slot on the Choice Band set.
Checks and Counters
Salamence and Gyarados resist both Bug and Fighting and have Intimidate to mitigate damage from Megahorn. Still, Heracross packs a huge punch, and Rock Slide hits both of them pretty hard. Skarmory takes about 30% from Brick Break and is not only 2HKOed by Focus Punch Heracross, but OHKOed by Guts and Choice Band variants. However, it does have an awesome base 140 Defense and 4x resistance to Megahorn, so most of the time it should be fine. Weezing resists Megahorn, can Haze away any boosts, and eliminate Heracross with Fire Blast, Flamethrower, or Sludge Bomb. It might run into trouble though, as it doesn't have a reliable way to recover, and if it uses Will-O-Wisp or poisons Heracross with Sludge Bomb, Guts will activate to make Heracross even more powerful. Additionally, Facade will 2HKO Weezing. Dugtrio can trap and take out Heracross with Aerial Ace; it's not going to take any hits and live, though, and loses to Endure + Salac Berry variants.
There's also Arcanine, who has Intimidate and resists Megahorn, but you seriously don't want to switch it in on any other attack. Moltres and Charizard resist Bug and Fighting as well, but are OHKOed by Rock Slide; similar considerations apply to Zapdos. Crobat 4x resists both Heracross's STABs and can OHKO with Flying moves, but must watch out for Rock Slide as well.