Blastoise-Mega @ Blastoisinite
Ability: Rain Dish
EVs: 180 HP / 252 SpA / 76 Spe
Modest Nature
IVs: 0 Atk
- Scald
- Rapid Spin
- Dark Pulse
- Ice Beam
Entei @ Choice Band
Ability: Pressure
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Sacred Fire
- Extreme Speed
- Stone Edge
- Flare Blitz
No fancy 'mons or sets here, but just a classic and strong core. Entei and Mega-Blastoise form a very good wallbreaking core, beating each other's counters.
Entei incinerates special walls (Blissey, Florges) that annoy Blastoise and kills the things that take advantage of the slow turtle: Grass types such as Rotom-C (outspeeding the Timid Specs set), Electric types (Galvantula and the frail Heliolisk get KO'd easily with ES, after some prior damage) and the very annoying Mega-Beedrill. Even if a check switches into Entei, it never appreciates to get burned and crippled.
On the other side, Blastoise beats Ground, Rock, Fire, Dragon mons that love to switch into Entei and physical walls that take little damage from it (Jellicent, Donphan, Slowking, Salamence). But then, why would you use Blastoise over any other Water-type ? Well, Blastoise has access to the coveted Rapid Spin, allowing it to remove the hazards that Entei HATES, while not removing our own hazards (in opposition to Defog). Entei really appreciates that, as it needs SR to get many KO's or 2HKO's.
The advantage of this core is that it is pretty self-sufficient, it doesn't need much help from it team. SR is helpful, cleric support is appreciated but not mandatory. Couple Entei and Mega-Blastoise with a good Grass type that beats Shitcune, such as Roserade or Rotom-C, and you have an excellent core that covers the entire tier.