With Little Cup being such a Speed-based metagame, Croagunk definitely has found its niche. With its amazing slew of strong priority attacks, Croagunk is one of the prime revenge killers and sweepers. Croagunk is also easy to fit onto almost any team since it boasts an invaluable Water immunity along with resistances to Dark, Fighting, Rock, Grass, Poison, and Bug to compensate for its mediocre defenses. This makes Croagunk a very reliable Pokemon, often capable of holding a team together under pressure. Croagunk may not sweep as often as some Pokemon, but its ability to check a large number of threats makes it a valuable asset to any team.
This set focuses on reliably revenge killing your opponent's sweepers. Croagunk has access to more priority attacks than anyone else in Little Cup, most notably Vacuum Wave and Sucker Punch. Fake Out allows Croagunk to hit a Pokemon twice before they attack once. This gives Croagunk the ability to revenge kill Choice Scarf users and most other Pokemon with a Speed boost (so long as they are not named Dratini!). Croagunk also has room for Ice Punch or Dark Pulse to hit Gligar and Ghost-types respectively.Team Options & Additional Comments >>>
This set's premise is quite simple: use Nasty Plot and sweep with Vacuum Wave. This set also uses Sucker Punch, making use of Croagunk's decent Attack. Sucker Punch also gives Croagunk a way to stop Ghost- and Psychic-type Pokemon from revenge killing it. Sucker Punch and Vacuum Wave together are nearly unresisted in Little Cup, aside from one popular Pokemon: Croagunk. Shadow Ball allows Croagunk to hit opposing Croagunk and Gligar for neutral damage, reliably hit Ghost-types with Substitute, OHKO Wynaut after a Nasty Plot, and have perfect coverage alongside Vacuum Wave.
Since bulky variants of Gligar won't mind switching into a neutral Shadow Ball, Ice Punch is a viable option. While not using the Nasty Plot boost, Ice Punch still reliably hits Ghost-types and hits Paras for super effective damage, as well as OHKOing Gligar. If Munchlax really troubles you, Low Kick can be used. It should be noted that using Low Kick takes away from Croagunk's sweeping power due to redundant coverage.Team Options & Additional Comments >>>
This set aims to take advantage of the classic Substitute and Focus Punch combination. Croagunk can come in on something that it can force out (such as a Choice locked Water move), and Substitute on the switch. Croagunk now gets a free STAB Focus Punch to smash the opponent’s face with. Ice Punch is used for Gligar and Drifloon only; a resisted Focus Punch will hurt more than a neutral Ice Punch on any other target. Sucker Punch is great on this set, as your opponents will be forced to attack to break your Substitute, almost eliminating prediction wars when using Sucker Punch. It’s also great for grabbing quick KOs on Pokemon who you fail to OHKO with Focus Punch.
The option of Muscle Band versus Life Orb comes down to personal preference. Just be aware that if you don't manage to heal Croagunk by switching into a Water-type attack, you can only Substitute three times at best with a Life Orb equipped.Team Options & Additional Comments >>>
A purely special Nasty Plot set can work decently for Croagunk; however, it is almost completely outclassed by the mixed set for a couple of reasons. The main advantage the pure Nasty Plot set would give is the ability to OHKO Munchlax with a +2 Hidden Power Fighting; however, lacking Sucker Punch means it can be revenge killed by everything that is faster and isn't KOed by Vacuum Wave which is quite detrimental to the set's viability. A Bulk Up set could work, but Croagunk does not really have the bulk (pun intended) to use it effectively; Croagunk is still easily OHKOed by many of the most common Croagunk counters such as Gligar.
On the physical side, Poison Jab was left out due to Poison having poor coverage, and having better available options. Other physical options include Rock Slide, X-Scissor, Brick Break, Earthquake, and ThunderPunch. However, these are lesser options on any set because many of the moves are needed for power, coverage, priority, and Gligar. Gunk Shot is an incredibly powerful Poison-type attack, but its shaky accuracy makes it not worth it.
Choice Band and Choice Specs are both viable options on Croagunk because of its above average attacking stats and great movepool. Additionally, Croagunk can still utilize its priority attacks on both sets. While it seems like a good option at first glance, it is rarely a good idea to be locked into Fighting-type attacks due to the presence of Ghosts-types and Gligar in the metagame. Additionally, being locked into priority attacks is a gamble as well; many Pokemon can easily set up on something like Bullet Punch or Sucker Punch.
Checks and Counters
Duskull and Gastly are really good counters. They can come in on anything Croagunk has to offer (barring the rare Shadow Ball, Dark Pulse, or Payback) and threaten it. Even if Croagunk packs Sucker Punch, Gastly can just put Croagunk to sleep with Hypnosis, while Duskull can burn it with Will-O-Wisp. Wynaut is also a great counter, since it can come in on any resisted or neutral attack except Nasty Plot and beat Croagunk. Wynaut can avoid Sucker Punch with Encore, though it should be noted that Counter will trigger Sucker Punch.
Tentacool resists both of Croagunk's STABs and has high Special Defense to sponge hits. Grimer can come in and set up Curse on Croagunk (as long as Croagunk does not have Earthquake). Koffing takes little from Croagunk's STAB attacks, is neutral to Dark, and has Will-O-Wisp and Flamethrower to counter the poisonous frog. Bronzor works well for countering priority Croagunk; however, it needs to be careful around SubPunch and Nasty Plot sets. Gligar can completely wall Ice Punchless Croagunk, and easily KO it with Earthquake. Diglett is a great revenge killer for Croagunk, with Arena Trap, and the ability to survive a Vacuum Wave and OHKO with Earthquake. Diglett does lose to the pure priority variant barring perfect Sucker Punch prediction.
Since Croagunk often relies on priority, using Pokemon who are faster than Croagunk and OHKO it with their own priority are great revenge killers. After Life Orb recoil, Pokemon such as Eevee and Zigzagoon OHKO Croagunk with Quick Attack and ExtremeSpeed respectively (as long as they carry a Life Orb of their own).