squirtle wartortle blastoise pokemon card Evolution Set - GX 35/214 - Sun Moon Unbroken Bonds Pokemon 151 Blastoise EX 200

The more powerful the format, the more effective this card tends to become

Thankfully, over the past decade, even Wizards has realized that partners are pretty broken, and now they avoid printing more cards with the mechanic, instead relying on various partner-with-style mechanics that do something similar but with a much smaller pool of cards to choose from, like how you can partner a Doctor's companion with a Doctor from the Doctor Who set

Poochyena and Mightyena are also solid evolutionary line here as well

Then once on your turn and once per turn, you can spend five life to grow her in size by three +1/+1 counters