With an Attack stat higher than that of Groudon, Zekrom, and Rayquaza, a respectable Speed tier, and a beefy base 150 HP stat, combined with great coverage moves such as Earthquake and Night Slash, Slaking looks like a top-tier Uber threat. That is, until you spot its ability, Truant, probably the single worst ability in the entire game. Because of Truant, Slaking becomes huge setup fodder for dangerous sweepers. It also keeps Slaking from having any way of sweeping the opposing team, even late-game. With such a letdown of an ability, Slaking is rather challenging to use. That said, it can and often will KO at least one of the opponent's team members if it gets a free switch in.
Even though its ability lets it down quite a bit, Slaking can still fill a role with its flagship hit-and-run strategy. Even though staying in more than a single turn is usually a terrible idea for Slaking, it can still effectively use that turn to deal out massive damage with a Choice Band-boosted hit. Thanks to its powerful STAB move alongside its coverage moves, there are not many Pokemon in NU that appreciate taking a hit from a Choice Banded Slaking, and with Pursuit, it can even outspeed and checkmate Jynx and Haunter.
Return is the STAB move of choice, as it has good Base Power with no drawbacks. Earthquake is the main coverage move, as it hits Rock- and Steel-types, which resist Return, for super effective damage. Night Slash rounds off the simple, yet effective coverage. Without Night Slash, Ghost-types such as Misdreavus, Haunter, and Golurk would be able to switch into Slaking much more safely. When it comes to choosing a move for the last spot, Pursuit is the preferred option, even though Retaliate might be more effective for Slaking's hit-and-run strategy. With Pursuit, Slaking can take out fleeing Psychic- and Ghost-types, most notably Jynx and Haunter, which can only outspeed Slaking when using a Choice Scarf. However, Retaliate is great for revenge killing, as very few Pokemon can switch into a boosted Retaliate and live to tell the tale.Team Options & Additional Comments >>>
Slaking really does not have many other notable items or moves it can utilize. However, Slaking does have three alternative STAB options: Double-Edge, Body Slam, and Giga Impact. Double-Edge is very similar to Return but has higher Base Power, and because Slaking has such a huge HP stat, it usually will not take large amounts of recoil damage. However, Double-Edge is illegal with Night Slash and will force you to run Shadow Claw, an inferior coverage option, instead. Body Slam is nice for extra utility alongside Pursuit, as it comes with a 30% chance to paralyze the opponent. Unfortunately, Slaking only gets to attack every other turn, which means it needs to make the most out of every turn it gets to attack with more powerful moves. Giga Impact might seem to fit perfectly with Slaking's ability and item, but it forces Slaking to stay in after attacking and should therefore almost never be used.
For coverage moves, Sucker Punch is a neat option, but it is also a risky one, especially when playing around potential Substitutes or setup moves, as it makes Slaking even easier to set up on. Other than that, Slaking has many coverage moves that it could utilize; Fire Punch, Ice Punch, and Low Kick are all options, but Slaking's main coverage moves will usually do the job much better. Slaking also has a decent Special Attack stat, so it can use special attacks to help break through tough physical walls; most notably, Thunderbolt and Fire Blast help it get past Alomomola and Tangela, respectively. Encore could be an option to deal with slower setup sweepers, such as Swords Dance Pinsir, but Slaking should usually use its turns to attack the opponent. When it comes to different sets, the only real other one that might work would be a set with Bulk Up and Slack Off, but due to Slaking's poor Special Defense stat and an ability that makes it hard to stay in even two turns, it is almost impossible to pull off successfully.
Checks and Counters
The single best way to deal with Slaking is Protect. If you have a Pokemon with Protect against a Slaking, it is impossible for it to hit you at all. Guts Pokemon, such as Swellow and Ursaring, can freely take advantage of Slaking's presence to activate their Status Orbs during Slaking's Truant turn. Additionally, Tangela and Alomomola are very bulky on the physical side and can easily avoid the OHKO from any of Slaking's moves. They can then put it to sleep or stall it with Toxic and Protect. Rock- and Steel-types such as Golem and Metang can easily take any STAB move but should be afraid of Earthquake. Similarly, Misdreavus is immune to Slaking's STAB moves and Earthquake, but Night Slash threatens it.
A different way of playing effectively around a Slaking is simply sacrificing an expendable Pokemon. After doing so, you receive a free turn that you can easily use to your advantage to set up for a sweep or place Stealth Rock. Be aware of Slaking's partners though, as the user should and often will be prepared for dangerous setup sweepers.