After searching out for recommendations to beat Single Battles in the Battle Maison I’ve found one that I’ve been successful with.
Kangaskhan @ Kangaskhanite
EV’s: 4HP / 252 Atk / 252 Spe
Nature Adamant (+Atk, – SpA)
– Fake Out
– Power-Up Punch
Gliscor @ Toxic Orb
Ability : Poison Heal
EV’s: 252 HP / 4 Atk / 252 Def
Nature Impish (+Def, – SpA)
– Aerial Ace (Sometimes Double Team can screw you over but not with this)
– Earthquake (for Steel-Types)
Chansey @ Eviolite
Ability: Natural Healer
EV’s: 4 HP / 252 Def / 252 SpDef
Nature Bold (+Def, -Atk)
– Seismic Toss
With this set Singles in the Battle Maison is pretty easy. Your biggest weakness is if Mega Kangaskhan goes down in the first turn. Otherwise he can pretty much hit anything for neutral damage, make sure his friendship towards you is maxed to get the most out of Return it still counts in the Battle Maison.
On your first turn I almost always run Fake Out unless I think I can KO the opposing monster with a Power-Up Punch after I’ve Mega-Evolved. If it’s a ghost I stay as regular Kangaskhan and use Fake Out then Mega-Evolve next turn to be sure I hit it with Scrappy.
Gliscor is your physical wall and does his job well. Your biggest weakness is to make sure whatever Pokémon you are facing doesn’t have an Ice-Type move. Otherwise the Toxic Orb and Poison Heal after you’ve inflicted Toxic on the opposing Pokémon use Protect and heal up. It’s wonderful.
Some people prefer Blissey over Chansey for the better stats but I find that if I just use an Eviolite Chansey I can literally survive anything that hits me with enuogh time to get a Toxic off. Now if instead you’d like a different attacking move than Seismic Toss you could evolve Chansey into Blissey give it Leftovers and throw on a Ice Beam or Flamethrower because Blissey has some Special Attack. Your choice though.
Here is another set that I’ve beaten the Singles Battle Maison with though I lost shortly after the 50th mark.
Greninja @ Life Orb
EV’s: 252 SpA, 252 Spd, 4 SpDef
Nature Timid (+Spd, -Atk)
Ferrothorn @ Leftovers
EV’s: 252 HP, 200, SpDef, 52 Def
Nature Relaxed ( +Def – Spd)
Garchomp @ Garchompite
EV’s: 252 Atk, 252 Spd, 4 HP
Nature Jolly (+Spd – SpAtk)
-Outrage / Dragon Claw
Strategy is pretty straightforward lead with Greninja and battle until he faints unless you can switch in and destroy someone with Ferrothorn but I normally stick with Greninja. Then switch in Ferrothorn and if he can’t cut it have Garchomp come in Mega-Evolve and wreck some stuff. Give it a shot!