Accelgor is definitely an interesting Pokemon. Aside from the fact that it doesn't evolve conventionally, as it evolves, its stat spread changes massively. A high Speed stat, an average Special Attack stat, and frail defenses would lead one to think Accelgor plays similarly to Electrode, but much like it, Accelgor has a rather interesting support movepool, which it utilizes brilliantly thanks to its incredible Speed. Accelgor may not have Taunt or Thunder Wave, but it does have access to Spikes. This makes it the fastest user of Spikes barring Deoxys-S, which is confined to Ubers. Despite all these traits, however, Accelgor is held back by its lack of presence. It could be OHKOed if you sneezed hard enough, and if it sneezed back, it would barely even tickle. That said, coming out of its shell was not all bad news for the gastropod.
Setting up Spikes is one of the most prominent benefits to a team. Quite often, due to the lack of Taunt or Encore, Accelgor will struggle to set up three layers of Spikes, but even one or two layers can show some results. Thanks to Focus Sash, this is always a possibility, as maximum Speed Accelgor can utilize its high Speed stat to set one layer of Spikes before the opponent uses Taunt. Against less aggressive leads, Accelgor can even attack, possibly weakening the opponent for the next attacker once Accelgor goes down. Bug Buzz provides good STAB, whereas Focus Blast gives even coverage. The EVs maximize Accelgor's Speed, which is of utmost importance, as it results in a worst-case scenario of a Speed tie.Team Options & Additional Comments >>>
Even though Accelgor may not have the offensive prowess of Raikou or Chandelure, it can still throw some punches with a Special Attack stat that matches that of Mew and Victini. However, Accelgor lacks their wide movepools and high, all-around stats, meaning it does lack some competitiveness. Despite this, Bug Buzz still makes for a strong STAB, and backed by Focus Blast, Accelgor actually has some good coverage. Hidden Power Ice will hit Ground- and Flying-types hard. Of course, it is still worth keeping in mind that Accelgor is no heavyweight, and is likely to only score a 2HKO before being blown away; playing Accelgor requires more caution than most other attackers. Like the ninja, the instant kill is not always the target, but incapacitating your opponent can be enough to allow for survival.
The fourth moveslot makes a small difference on the set overall, but is still a considerable choice. Acid Spray is the most highly recommended option, despite its poor type coverage and low Base Power. It may not seem like much of a threat at first glance, but Accelgor can often force a switch, and by hitting the switch-in with Acid Spray and lowering their Special Defense, it may force even more switches, racking up entry hazard damage, or allow Accelgor to deal more damage, suddenly bringing a larger number of Pokemon into an OHKO range for Accelgor's attacks. Giga Drain is an option over Energy Ball, as the small change in damage output is negligible for power as low as Accelgor's, but the regain in health, especially that lost from Life Orb recoil, can make quite a difference. U-turn can be quite an effective opening move also, allowing Accelgor to scout for a switch and do a small amount of damage on the way out.Team Options & Additional Comments >>>
Hydration and Rest can be somewhat effective, as Accelgor learns Rain Dance, which can also support an entire team. However, being OHKOed and 2HKOed by nearly everything makes Hydration and Rest a poor idea, even though Rain Dance itself can have its uses. Accelgor's extremely low defenses plague it again in that it has trouble putting its incredible support movepool to good use; Baton Pass, Encore, Recover, and Substitute are too difficult to use, especially when Accelgor already has access to the extremely useful Spikes. Offensively, Energy Ball and Sludge Bomb are the only options not listed worth using.
Investing in Accelgor's bulk is similar to driving a car with your teeth. Don't do it. If it isn't outspeeding things to set up Spikes, it should be hitting as hard as it can—base 100 Special Attack is still rather poor. Accelgor doesn't really need support from its teammates, as its own job is normally to set up Spikes and die. The best teammates for it would be anything that can hit hard and hit quickly, or stall and shuffle the opponent's team. That way the Spikes it dropped won't go to waste.
Checks and Counters
Accelgor is more of a supporting Pokemon, and so its list of counters is less than a sweeper. On top of this, its ridiculous Speed means that one of the few sure-fire stops to a supporter, Taunt, becomes less effective, as very few Taunt users can outpace Accelgor without Prankster or a Choice Scarf. Alternatively, a hard-hitter can hope to KO Accelgor before it can fully finish its job. Without a doubt, Stealth Rock and other entry hazards are your greatest tools. Stealth Rock alone will not only invalidate Accelgor's Focus Sash, but also bring it down to 75% health. From here, KOing it with any priority is a simple task. Weavile, Azumarill, and Mamoswine have strong priority attacks, but avoid using Machamp or Hitmontop, as a resisted hit, even on something as frail as Accelgor, will not do as much damage.
If you are genuinely struggling to rid yourself of Accelgor, then Crobat and Aerodactyl are able to Taunt with reasonable speed, and then follow up with a strong attack, especially as they resist Accelgor's main attack. However, dealing with an offensive Accelgor proves slightly more difficult. Accelgor's low attack power doesn't seem like a threat, but its coverage will allow it to score some cheap damage, making your counter less of a threat later on. Mismagius, Arcanine, and Darmanitan all resist Accelgor's attacks and can hit back with their high-damage moves. However, they are rather slow compared to Accelgor, so don't expect to be taking it down cleanly. It is impossible to outspeed Accelgor without using Ninjask or a Choice Scarf, and so if you do attempt to KO it to prevent your opponent from gaining an advantage with Spikes, you may end up revealing a surprise Choice Scarf user. Despite this, Accelgor doesn't provide a large number of problems while it is in play, and as long as you have a Rapid Spin user, you can afford to let it waste time setting up Spikes before killing it.
Accelgor doesn't need more Speed.