[OVERVIEW]
Heracross has a decent SpDef stat Special Defense and a really high Attack, which lets it take quite a few special hits on the Special side and fire back hard on the Physical side physically. Its Bug typing is both a blessing and a curse, meaning it can allows it to switch into the very common Earthquake easily, which effectively checks Nidoking and Steelix, for example, since they rarely pack any Fire-type moves. (effectively checking Nidoking and Steelix, for example, since they rarely pack any Fire-type moves) but However, this also leaves his its only prominent STAB move resisted by very common types, (AC) such as Flying and Steel.
[SET]
Set 1: SleepTalk
Item: Leftovers
Move 1: Rest
Move 2: Sleep Talk
Move 3: Megahorn
Move 4: Curse / Seismic Toss
[SET COMMENTS]
Heracross has quite the shallow movepool and but a decent combination of bulk and typing, which makes RestTalking the perfect strategy for it. Megahorn is the 120 Base Power STAB nuke, which a 120 BP STAB move that heavily dents anything that doesn't resist it. Curse and or Seismic Toss rounds up the set, (AC) providing respectively late game either late-game sweeping power and or a better way to hit Skarmory so another teamate (like Marowak or DrumLax) teammate like Marowak or Drumlax has an easier time taking it down.
Unfortunately, most things Pokemon that do resist the main move Megahorn like Zapdos and Skarmory are quite common and shut Heracross down quite easily, like Zapdos and (especially) Skarmory, so getting rid of its common checks is crucial for Heracross to shine. Even Seismic Toss only does 30% to Skarmory and even less to Zapdos, so even if you get them on the switch, it's usually best to just switch Heracross out.
[Other Options]
Earthquake provides really good coverage, since it hits things like Gengar, Nidoking, (AC) which otherwise might stay in to deal chip damage, (AC) (who otherwise might stay in to chip Heracross) and Raikou, (AC) which gets 2HKOed by it, (AC) and Gengar (practically securing the 2HKO that Megahorn almost always fails to get) super effectively, but it does nothing to combat Hera’s Heracross's main problem of Zapdos and Skarmory being unbreakable, so the main set is usually better.
You Heracross can opt to have a Curse+3 attacks (Megahorn, Earthquake and Hidden Power Rock) for a set utilizing Curse, Megahorn, Earthquake, and Hidden Power Rock if you want to exchange staying power for offensive pressure. This set works like a poor man's Curse Machamp, (RC) with better special bulk and key resistances, but it has a worse STAB move and is still hard walled by Skarmory, like the main set.
An Endure + Reversal (added spaces) set is marginally viable, but Heracross isn’t fast enough for it to be consistent, not to mention it’s only a one-time use if Spikes are in play.
[Checks and Counters]
Skarmory is the best defensive check, while Zapdos is the best offensive one, but. (add period) Charizard and Dragonite, though far less prominent, are safe switch-ins too for almost all Heracross, bar less viable Hidden Power Rock sets. Keep in mind that Dragonite must have super effective moves, (AC) or Heracross might chip it down. Steelix can’t do much besides trade with Explosion or phaze with Roar it out, but it’s hard to break through and takes 5 five Seismic Tosses to KO (Earthquake does roughly the same damage, but far less if Steelix already has a Curse under its belt, which is usually does). Miltank can switch in safely enough and Growl your damage and/or lower Heracross's Attack with Growl as well as curse pp Curse PP (not sure what this means tbh) away while healing up with Milk Drink, but it can't really damage Heracross. Gengar is immune to Seismic Toss, takes negligible damage from Megahorn, (AC) and can threaten Heracross with Explosion or Destiny Bond, but it must watch out for Earthquake if it doesn't want to trade, (AC) and Curse sets can mitigate the danger of Explosion while helping with DBond mindgames Destiny Bond mind games. Do note that unless Gengar is carrying the rare Fire Punch, it cannot force Heracross out without threatening to also faint. Heracross can check itself, but it's not recommended unless you're ok with starting willing to start a pp war (replace this with whatever it's supposed to mean) with your opponent or you're if your Heracross is packing Curse and they're theirs is not.