Crackdown Construct + Crypt Rats

Crackdown Construct
Crypt Rats

Requires
Crackdown Construct must be on the battlefield. Crypt Rats must be on the battlefield.
Steps
  1. Activate Crypt Rats by paying 0.
  2. Crackdown Construct triggers, giving itself +1/+1 until end of turn.
  3. Repeat.
Results
Infinitely large Crackdown Construct until end of turn.