Totem Gumshoos (SM battle)

Note: This fight is exclusive to Pokémon Sun.

Enemies
A Lv. 12 Gumshoos is the Totem Pokémon here. For some reason, it has Adaptability of all things as an ability, as well as the Pecha Berry as a held item, which cures Poison. It knows the moves Super Fang, Bite, Leer and Scary Face. The aura increases Totem Gumshoos's Defense stat by one stage when the battle begins. When a turn passes by, a Lv. 10 Yungoos with the moves Tackle, Pursuit, Leer and Bide, is summoned. In addition, this shifty mongoose also has Stakeout, which boosts the power of its attack if the opponent just switched in halfway through the turn. When combined with Pursuit, well... Good thing that when it faints it can't be called again.

Ideal Pokémon
If it knows a Fighting-type move, it's good for this fight. Yes, that even includes Pikipek, who learns Rock Smash. Rock Smash also happens to have a chance of lowering the opponent's defense, which is Gumshoos's boosted stat. Pikipek's frail defenses, however, means that it can't do much. Cross your fingers in hopes that it and its ally use a non-damaging move or Super Fang. There's a chance of 6 in 16 of them doing that, though, and luck can only be pushed so far before it runs out. If you just want to go all-out, teach it Brick Break, but I think the Fighting-type Pokémon can put it to better use.

Additionally, the Fighting-type Pokémon are solid choices. If you want one, it's either Crabrawler or Machop. Both of them have decent bulk and great Attack. Crabrawler in particular is faster than everyone in the fight, and it becomes a terror if it pulls enough Power-Up Punches. Machop doesn't have that extra bit of speed, but if you grind it up to level 13 (pretty easy because it's a traded Pokémon) it gets Low Sweep, a potent Fighting-type move, but if you want to save up some effort, you can teach it Brick Break right away. It's all up to personal preference.

The Ghost-types from Hau'oli Cemetery might seem tempting choices, since they are immune to Normal-type moves, but if you look at their bulk (specially that of Gastly)... IT'S NOTHING. Really hurtful, considering that Gumshoos knows Bite and has a very high attack. However, Drifloon is still useful due to having the Aftermath ability, which hurts opponents if Drifloon faints, having absurd HP, decent special attack and very good speed, as well as knowing Gust.

But the unsung hero of this battle has to be Magnemite. It has very high Special Attack, which already puts it at an advantage because Gumshoos has a weak special defense, and Magnemite also has high defense as well as the gift of resisting Normal-type moves due to being a Steel-type, despite its low HP. Not only that, but it also gets Thunder Wave, a status move that paralyzes. Yes, you got it at an earlier point of the game... but you can grind it up and make it fit in your team.

Strategy
This fight can be a decent challenge if you're not prepared enough, but it's not too difficult. Focus on chipping away at Gumshoos and don't use physical attacks unless it's a fighting-type move. If you ever feel the need of switching out, defeat the Yungoos first, then switch out. But even then, that's wasting two turns you could have used on attacking Gumshoos. If you spam Power-Up Punch with Crabrawler, you can do some serious damage to Gumshoos. If you did the math, it turns out that Gumshoos goes down in two Power-Up Punches, counting the attack boost after the first one. Machop and Makuhita aren't much worse, and Makuhita knows Arm Thrust, which is excellent for this fight. You can also use the fact that it doesn't heal on your favor. So defeat the Gumshoos first, and then take on Yungoos.

Using any status ailment excluding poison can also favor you in battle. Using Magnemite with Thunder Wave will lead you straight to victory, although a more reliable method would just be the above strategy.