So...first, for the people who say SwagPlay has little to no counters because anything else can be beaten through hax, just stop it. Sure, few pokemon other than stuff like Roost Xatu are 100% counters, but there are still pokemon all over that have a good chance of winning. It's like saying Weavile is broken because it can beat nearly any pokemon by outspeeding, Ice Punching and getting a freeze. Yeah, in theory that's true, but that's a ridiculous chance to rely on. There are a lot of good counters that people have pointed out that aren't 100% but work well. Here are a few more:
Magnezone: High (base 115) physical defense, while having a low (base 70) attack stat that it doesn't use and can therefore lower it all the way down to 0 IVs. Immunity to Thunder Wave. Substitute sets are decently viable due to being able to set up on Ferrothorn, Forretress, some Jirachi, etc. and dump on swagger sets too now. Volt Switch can break subs and remove swagger in the same turn. Finally, it can do all that while trapping Klefki, who is generally considered the best Swag Player.
Tangrowth: Similar to Magnezone, it can be physically defensive while using only special attacks though some like to go physical attacking or mixed. Admittedly Earthquake takes out Klefki a lot easier, and Knock Off puts a limit on number of substitutes. If swaggers stack up too much, switch and you can heal off whatever you took with regenerator.
Zygarde: Specifically, Coil Zygarde. Coil can get defense boosts to keep up with attack somewhat, which makes it hard to get revenged by Ditto unless you have Outrage, not recommended on a slow coil set, and naturally high defense means it isn't too badly hit by confusion or foul play. Zygarde is immune to Thunder Wave, and benefits from Swagger. Most importantly, if you can get confusion to end without dying first, +2 or +3 Extreme Speed murders swagplay.
Other people have already pointed out good ones: Mandibuzz, Rotom-W, Chansey, Clefable, Xatu, Sylveon, Umbreon, Thundurus, Quagsire off the top of my head. Other things like Lum Berry too, that aren't even a specific pokemon.
If you're not prepared for a certain threat, you're gonna get beat. And for the people who say that one counter can't take on a team of six, well, odds are it can take on a few and the rest of your team can luck through if you're up 5-3 or whatever when your best counter goes down. Or, ya know, it is a legitimate strategy to overwhelm the opponent with pokemon that use similar checks to wear them down so eventually one of them gets through. That's the entire idea behind cores like Staraptor+Talonflame, and 2Drag+Mag or whatever it was called.
Second, the burden of proof for why this should be banned is on the people banning. Smogon doesn't just ban stuff because "no one" likes it or uses it, or it's deemed not viable.
Third, about the dependence of luck and lack of skill...well, that's not exactly all that much more abundant in Swagplay than other teams. You still need to analyze what the opponent can do to you. If you're up against Mandibuzz and aren't getting anywhere, maybe you should switch to an actual attacker. If Gardevoir can hit your Liepard with Hyper Voice, gtfo.
I know it sounds a lot simpler than other styles but, really, that's probably because you're used to facing teams that are six of the same one trick pony swagplayers who all do equally well (or bad, most likely) against any pokemon. A well built swag play team with 2-3 abusers, and other pokemon that cover its flaws actually does take skill and will be a lot more successful.
As for reliance on luck...a few people have pointed this out, but against an opponent with confusion and paralysis, luck is actually on the annoyers' sides. It's about the long run odds. Landing that first swagger is the hardest part, especially if the opponent is particularly threatening (though that's when Ditto comes in...) From there, you can use substitute and have a decent chance of buying yourself a free turn, even better chance if the opponent is paralyzed. Switching also gets free subs, so swagplay will work more often than not, at least if you're looking for free turns to safely land foul play or set up spikes or whatever.
Also, it doesn't take luck to boost attack and use foul play, the only part requiring luck is getting free turns, and they'll happen time to time, that's just how chance will work. It doesn't really matter when the free turns come if you're spamming substitute and fishing for them.
Magnezone: High (base 115) physical defense, while having a low (base 70) attack stat that it doesn't use and can therefore lower it all the way down to 0 IVs. Immunity to Thunder Wave. Substitute sets are decently viable due to being able to set up on Ferrothorn, Forretress, some Jirachi, etc. and dump on swagger sets too now. Volt Switch can break subs and remove swagger in the same turn. Finally, it can do all that while trapping Klefki, who is generally considered the best Swag Player.
Tangrowth: Similar to Magnezone, it can be physically defensive while using only special attacks though some like to go physical attacking or mixed. Admittedly Earthquake takes out Klefki a lot easier, and Knock Off puts a limit on number of substitutes. If swaggers stack up too much, switch and you can heal off whatever you took with regenerator.
Zygarde: Specifically, Coil Zygarde. Coil can get defense boosts to keep up with attack somewhat, which makes it hard to get revenged by Ditto unless you have Outrage, not recommended on a slow coil set, and naturally high defense means it isn't too badly hit by confusion or foul play. Zygarde is immune to Thunder Wave, and benefits from Swagger. Most importantly, if you can get confusion to end without dying first, +2 or +3 Extreme Speed murders swagplay.
Other people have already pointed out good ones: Mandibuzz, Rotom-W, Chansey, Clefable, Xatu, Sylveon, Umbreon, Thundurus, Quagsire off the top of my head. Other things like Lum Berry too, that aren't even a specific pokemon.
If you're not prepared for a certain threat, you're gonna get beat. And for the people who say that one counter can't take on a team of six, well, odds are it can take on a few and the rest of your team can luck through if you're up 5-3 or whatever when your best counter goes down. Or, ya know, it is a legitimate strategy to overwhelm the opponent with pokemon that use similar checks to wear them down so eventually one of them gets through. That's the entire idea behind cores like Staraptor+Talonflame, and 2Drag+Mag or whatever it was called.
Second, the burden of proof for why this should be banned is on the people banning. Smogon doesn't just ban stuff because "no one" likes it or uses it, or it's deemed not viable.
Third, about the dependence of luck and lack of skill...well, that's not exactly all that much more abundant in Swagplay than other teams. You still need to analyze what the opponent can do to you. If you're up against Mandibuzz and aren't getting anywhere, maybe you should switch to an actual attacker. If Gardevoir can hit your Liepard with Hyper Voice, gtfo.
I know it sounds a lot simpler than other styles but, really, that's probably because you're used to facing teams that are six of the same one trick pony swagplayers who all do equally well (or bad, most likely) against any pokemon. A well built swag play team with 2-3 abusers, and other pokemon that cover its flaws actually does take skill and will be a lot more successful.
As for reliance on luck...a few people have pointed this out, but against an opponent with confusion and paralysis, luck is actually on the annoyers' sides. It's about the long run odds. Landing that first swagger is the hardest part, especially if the opponent is particularly threatening (though that's when Ditto comes in...) From there, you can use substitute and have a decent chance of buying yourself a free turn, even better chance if the opponent is paralyzed. Switching also gets free subs, so swagplay will work more often than not, at least if you're looking for free turns to safely land foul play or set up spikes or whatever.
Also, it doesn't take luck to boost attack and use foul play, the only part requiring luck is getting free turns, and they'll happen time to time, that's just how chance will work. It doesn't really matter when the free turns come if you're spamming substitute and fishing for them.