Swellow has not changed much throughout the passing generations, as its true potential has always rested in its ability, Guts. When Guts is activated, Swellow can clean up weakened teams, and being one of the fastest Pokemon in NU makes it difficult for it to be outsped. However, Swellow is very easy to stop, as its lack of coverage and low bulk make it an easy target. Swellow's Stealth Rock weakness and its vulnerability to priority attacks also make it increasingly difficult to use; even though it packs a punch, a lot of Pokemon can tank Swellow and KO it in retaliation. Additionally, the combination of Toxic Orb's effect, Brave Bird, and its frailness allow it to be easily worn down. Also, Swellow has difficulty defeating many Rock- and Steel-types in the tier alone, so it often relies on team support to get past them.
Swellow plays the role of a hit-and-run Pokemon. It works best as a mid-game sweeper because while Guts increases Swellow's strength, it doesn't quite have the raw power to OHKO everything in sight; preferably, enemies should be weakened beforehand. To avoid being weakened, Swellow can get a free switch in to activate Guts from a slow U-turn or Volt Switch, a predicted double switch, and/or when one of its teammates is KOed. Toxic Orb is then activated, though it puts Swellow on a timer and forces it to switch out often to avoid cumulative damage.
Facade is Swellow's main STAB move; after Toxic Orb's effect and the STAB boost add up, it reaches an amazing Base Power of 210, OHKOing Tauros and Rotom-S. Brave Bird is also Swellow's STAB move, and while the recoil damage can be harmful, it allows Swellow to hit Ghost-type Pokemon such as Misdreavus, Haunter, and Golurk. U-turn allows Swellow to pivot into a counter of the opponent, maintaining momentum for the user. Because Swellow cannot stay in long, it will often use U-turn after every attack or two. Quick Attack is Swellow's final move; while it is usually looked down upon, it does a good job in revenge killing weakened threats, and having priority can be useful. It also allows Swellow to dodge Sucker Punch from virtually every user, as Swellow outspeeds all of them.Team Options & Additional Comments >>>
A SubRoost set is viable, as it is great at keeping Swellow alive, but it should only be used with a Flame Orb because the damage from a Toxic Orb would pile on increasingly over time, and you wouldn't be recovering HP in the long run. Swellow can utilize Scrappy and a Choice Band to hit Ghost-types, but Facade is weakened, forcing it to rely on Return, a weaker Normal-type STAB. A set with Endeavor is plausible, but it needs good prediction to be successful. Toxic can be used to hit physically bulky Pokemon that switch into Swellow. Finally, there are a few lesser attacking options, notably Steel Wing and Pursuit, but Swellow has trouble fitting them into a set. There are very few other options Swellow should take, and it shouldn't drift from its standard set.
Checks and Counters
Stealth Rock is a great way to weaken Swellow, so Pokemon that can set it on the field successfully, such as Golem, Regirock, and Carracosta, are useful in defeating Swellow. Overall, any relatively strong Rock-type can take multiple hits from Swellow and KO it, making the majority of them good counters. Steel-types, specifically Klang, can tank Swellow's attacks and set up on it, making them good counters against Swellow as well. Metang also completely walls Swellow and can even hit it hard with its priority move, Bullet Punch. Bulky Pokemon that can take Swellow's attacks, stall it out, and retaliate back are good counters against it; Misdreavus, Golurk, Alomomola, Lickilicky, and Eelektross all fit in that category.
Choice Scarf users are one of the best ways to KO Swellow; Primeape, Sawk, Braviary, Jynx, Rotom-S, and Zebstrika are all examples of Pokemon that can outspeed Swellow and aim towards its frail defenses. However, be aware that most of them cannot switch into any of Swellow's attacks. Choice Scarf Haunter gets a special mention; it's a good check to Swellow because it outspeeds it and can't be touched by Quick Attack. Priority, excluding Sucker Punch, can severely weaken Swellow, especially when the opposing Pokemon can take a hit. Floatzel and Samurott are examples of priority users that can KO Swellow. All in all, any strong Pokemon that can take a hit can KO Swellow, as is not bulky. Wearing it down is also a way to KO Swellow, as without recovery, Stealth Rock, Toxic Orb's poison, and Brave Bird will quickly weaken Swellow. In particular, Ghost-types force Swellow to use U-turn or Brave Bird, which would wear it down even further.