Overview
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Statistically, Swampert has great stats everywhere it needs them. Its Mega Evolution has power rivaling that of the other powerful Mega Evolutions in the tier, and with Swift Swim, it's easily one of the fastest Pokemon in the metagame under rain. It is also very bulky with a great defensive typing that gives it a lot of resistances and only one relatively uncommon weakness. However, when looking past its stats, it becomes evident that Swampert is an otherwise average sweeper. It has everything it needs to hit a large portion of the metagame for a lot of damage, including a STAB spread move and a powerful, reliable STAB attack that can be further boosted by rain, though (I think this sounds better as "but", but up to you) its movepool doesn't provide it with much more than that. Also, unfortunately, Swampert is very reliant on rain, as it is slow outside of it. It is also weak against common Grass- and Water-types, (remove comma) and thus does nothing to help its team beat traditional rain counters. It doesn't have any reliable moves to boost stats, either, and its main attacking moves are also kind of weak in Base Power, (though the rain boost somewhat makes up for that in Waterfall's case.)
Swift Swim Sweeper
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name: Swift Swim Sweeper
move 1: Waterfall
move 2: Earthquake
move 3: Ice Punch / Superpower
move 4: Protect
ability: Damp
item: Swampertite
evs: 168 HP / 252 Atk / 88 Spe
nature: Adamant
Moves
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Waterfall is a reliable STAB move that is quite powerful, (remove comma) and even has the ability to flinch cause its target to flinch. Earthquake is a powerful STAB spread secondary STAB move that is also very reliable. Ice Punch gives coverage by hitting Dragon- and Grass-types super effectively. Be mindful that neutral Waterfall in rain hits harder than x2 2x super effective Ice Punch, so if the opponent foe doesn't resist Waterfall, use that instead. (unless Ice Punch is x4 super effective.) (implied imo? but if you want to keep it change x4 to 4x!) Superpower can also be used in situations where hitting Mega Kangaskhan is necessary, and it OHKOes a bit more than 40% of the time. It also hits Ferrothorn hard, but apart from that it isn't really useful. Protect protects Swampert for a turn when it Mega Evolves and also stalls against Grass-types to give partners more time to take threats out. Don't use it too much though, or rain turns will run out.
Set Details
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Swampert's EVs are quite easily tweaked based on what you need Swampert to outrun. 88 Spe lets it outpaces 252+ Mega Gengar (base 130) and everything slower, (remove comma) and is the standard spread. 152 Spe lets it beats Mega Sceptile and all Adamant Choice Scarf Landorus-T and below so you don't have to worry about Speed creeping. 224 Spe is pretty much as far as anyone needs to go, outspeeding maximum Speed Jolly Choice Scarf Landorus-T, (remove comma) and everything slower. After that, Attack is maxed out maximized for as much power as possible, and the rest of the EVs are put into bulk. Mega Swampert can survive pretty much any non-super effective attack as long as it's not boosted past +1. Swampert's initial ability should be Damp so that it can prevent Landorus-T from using Explosion before it Mega Evolves.
Usage Tips
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Mega Swampert works best under steady rain, where its Speed is boosted and the power of its Waterfall is multiplied by x1.5. Under rain, it can clean up weakened teams with its powerful spread Earthquake, or it can punch holes in frailer teams with its powerful Waterfall, using Ice Punch for coverage. With a partner to weaken tanks and remove Grass-types, Mega Swampert becomes a lot more difficult to stop. Early on, it is encouraged to use Protect to give Swampert a free turn to Mega Evolve and net the Speed boost. While playing, generally avoid trying to confront healthy physical tanks unless you Swampert can hit them super effectively. If there are priority users in the opposing team, try to keep Swampert healthy for endlate-game. Later on, a more reckless playstyle will allow Mega Swampert to deal as much damage as possible so that a partner can come in and clean up. If kept healthy, Mega Swampert can deal a lot of damage at this stage(comma) as it is very hard to OHKO without the use of Grass-type attacks. Avoid Grass-types unless you have Swampert has a partner that can remove them or they are in KO range of Ice Punch. Don't be afraid to switch out when in danger.
Team Options
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Politoed is pretty much 100% necessary to provide easily-accessed steady rain for Mega Swampert. Especially, Damp Rock is recommended so the rain turns can be prolonged as much as possible. Aside from Politoed, answers to rain counters are also very necessary, as Mega Swampert only compounds upon the weaknesses of its team. Flying-types such as Talonflame, Shaymin-S, and Togekiss are very appreciated, (remove comma) and form strong cores with Swampert. They help remove Grass-types while still allowing Swampert to freely use Earthquake, and they appreciate Swampert's ability to take down Electric- and Rock-types. Talonflame also helps against sun, Shaymin-S beats Rotom-W, and Togekiss provides redirection. Grass-types are good partners as well because they can beat Rotom-W and other bulky Water-types. Examples include Ferrothorn, Shaymin-S, and Ludicolo, the last of which can also utilize rain to form a powerful sweeping core with Swampert. Dragon-types help a lot(comma) as they cover Swampert's Grass-type weakness and lure in Steel-types for it to beat. Also, many of them are naturally immune to Ground and do not limit Swampert's ability to use Earthquake EQ. Pokemon like such as Latios, Salamence, Hydreigon, and Kyurem-B (though it is not immune to Ground) all make solid partners for Mega Swampert. Finally, Thundurus-I (don't need it for the base forme) makes for a great partner, switching into Grass-type attacks and hitting bulky Water-types, all the while being able to check Mega Charizard Y switch-ins with Prankster Rain Dance.
Other Options
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Rock Slide or Stone Edge can also be used as coverage. Aqua Tail can be used instead of Waterfall for more power at the cost of reliability and the chance to induce a flinch. Substitute can be used to protect Mega Swampert from status moves and allow it to take advantage of the switches it causes. Low Kick can be used as a substitute for Superpower, as it doesn't lower Swampert's stats and hits Mega Kangaskhan and Ferrothorn for 100 Base Power, which is still sizable damage (but not enough to OHKO). Wide Guard can be used for support. Facade is a possibility just in case Mega Swampert gets poisoned / or burned. A non-Mega support set with Wide Guard also has a small niche as a bulky Water-type.
Checks and Counters
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**Typing Advantage**: Typical rain checks and counters tend to handle Mega Swampert easily. Swampert has trouble dealing with bulky Water-types, especially Rotom-W, which it cannot hit neutrally besides with Superpower. Other Pokemon such as Suicune and Jellicent can sponge Earthquakes fairly easily and burn Swampert with Scald. Ludicolo in particular is a huge threat(comma) as it can shrug off any of Swampert's attacks in the rain and OHKO with Giga Drain. Gyarados is only hit neutrally by the weaker Ice Punch and even has Intimidate to weaken Swampert. Some bulkier Grass-types, such as Amoonguss and Ferrothorn, can give Swampert trouble as well, shrugging off an Ice Punch and OHKOing with a STAB Grass-type attack. Amoonguss can also redirect and absorb Swampert's Water-type attacks, making it difficult for Swampert to exert Swampert's its full offensive force. Mega Venusaur is even bulkier than Amoonguss and can KO with Giga Drain, recovering all health lost.
**Intimidate and Burns**: Intimidate hinders Mega Swampert. The most common Intimidate Pokemon in the metagame, Landorus-T, cannot safely switch into Swampert for fear of super effective Waterfall, but other Pokemon such as Hitmontop and Scrafty can switch in fairly safely to lower Swampert's Attack stat. Hitmontop can also use Wide Guard to block Swampert's Earthquakes, allowing even more possible opponents foes (opponent refers to the battler) to wall it. Gyarados doesn't have much to fear and can gradually wear Swampert down with continuous uses of Waterfall. Burns hurt as well, (remove comma) and can come from users such as Jellicent and Gourgeist-S or Gourgiest-S. Rotom-W again must be mentioned because it solidly counters Swampert with its typing, ability, and access to the crippling Will-O-Wisp. It Swampert most fears burns from Scald and burns form from priority users such as Sableye, which quickly nullify its power before it can react.
**Opposing Weather**: Swampert is very reliant on its weather, so naturally anything that can remove the effect of the rain is a threat to Swampert. Sun teams are very threatening to Mega Swampert, especially if Politoed is not in the sidelines to be able to reset the weather condition upon switching in, so sun sweepers such as Mega Charizard Y and Venusaur can easily remove Swampert with a super effective Grass-type attack. Sand is also fairly threatening, though not as much as sun because Swampert still retains a typing advantage against popular sand sweepers such as Excadrill, and the tier's main sand inducer, Tyranitar, fares horribly against Swampert 1v1. That said, the removal of Swampert's massive Speed boost still cripples it, making it easier for partners foes to take down. Abomasnow is also very troublesome, easily tanking all of Swampert's moves(comma) and removing its rain(comma) and OHKOing with Giga Drain.
**Speed Control**: Although Swampert is immune to Thunder Wave (and therefore the most common form of paralysis), other speed control techniques can still be used to cripple Swampert and make it easier to take down. Icy Wind hinders it by slowing it down so some of the faster Pokemon such as Shaymin-S and Mega Sceptile can outspeed it and take it down. Tailwind from Pokemon such as Suicune can be used to level the playing field and boost partners up past Swampert's Speed for a few turns. Trick Room can be used to give slower Pokemon an advantage, and it works especially well because Swampert is so fast in rain. Most Trick Room setters are also considerably naturally bulky, and common Trick Room support Pokemon such as Amoonguss can be used to KO Swampert quickly. Jellicent deserves an honorable mention(comma) as it can burn Swampert and only takes significant damage from the spread-reduced Earthquake, and Gourgeist-S can tank Ice Punch to 2HKO with Seed Bomb.
