Toxapex, primarina, Tapu lele, Celesteela
And Sandslash hits all of these super effectively, except Toxapex, which can't touch Sandslash.
Primarina: STAB Iron Head; resists all of it's moves
Tapu Lele: STAB Iron Head; only hit neutrally by Psychic
Celesteela: STAB Icicle Crash; hit neutrally by Heavy Slam and Flash Cannon
Defensive Calcs
252+ SpA Tapu Lele Psychic vs. 0 HP / 156 SpD Sandslash-Alola in Psychic Terrain through Light Screen: 48-57 (32 - 38%) -- 91.1% chance to 3HKO
252+ SpA Primarina Sparkling Aria vs. 0 HP / 156 SpD Sandslash-Alola through Light Screen: 46-55 (30.6 - 36.6%) -- 65% chance to 3HKO
0- Atk Toxapex Liquidation vs. 0 HP / 0 Def Sandslash-Alola through Reflect: 16-20 (10.6 - 13.3%) -- possible 8HKO
4 SpA Celesteela Flamethrower vs. 0 HP / 156 SpD Sandslash-Alola through Light Screen: 111-132 (74 - 88%) -- guaranteed 2HKO
Offensive Calcs
252+ Atk Life Orb Sandslash-Alola Iron Head vs. 252 HP / 4 Def Tapu Lele: 205-244 (115.8 - 137.8%) -- guaranteed OHKO
252+ Atk Life Orb Sandslash-Alola Iron Head vs. 252 HP / 4 Def Primarina: 103-122 (55 - 65.2%) -- guaranteed 2HKO
252+ Atk Life Orb Sandslash-Alola Earthquake vs. 252 HP / 252+ Def Toxapex: 55-65 (35 - 41.4%) -- guaranteed 3HKO
252+ Atk Life Orb Sandslash-Alola Icicle Crash vs. 252 HP / 0 Def Celesteela: 86-101 (42.1 - 49.5%) -- guaranteed 3HKO
First thing you'll notice: you should ALWAYS have AV up. There's no reason not to. And as long as Hail is up, you should be able to outspeed all of these.