Yuna, Grand Summoner + Freed from the Real

Prerequisites

You have a creature card in hand with the mana to cast it minus one colored mana.

Steps

1. Activate Yuna by tapping it, adding {U} and causing the next creature spell you cast to enter the battlefield with two additional +1/+1 counters on it.
2. Activate Freed from the Real by paying {U}, untapping Yuna.
3. Repeat an arbitrarily large number of times.
4. Active Yuna by tapping it, adding one mana of any color and causing the next creature spell you cast to enter the battlefield with two additional +1/+1 counters on it.
5. Cast any creature spell by casting its mana cost, triggering Yuna an infinite number of times, causing that creature to enter the battlefield with infinite +1/+1 counters on it.