Cast Wildwood Scourge by paying {1}{G}, causing it to enter with a +1/+1 counter on it.
Enduring Scalelord triggers, putting a +1/+1 counter on itself.
Wildwood Scourge triggers, putting a +1/+1 counter on itself.
Repeat from step 2.

Infinite +1/+1 counters on certain creatures

Wildwood Scourge

Enduring Scalelord

Cast Croaking Counterpart by paying {1}{G}{U}, creating a token copy of Wildwood Scourge that is a 1/1 Frog.
Put a +1/+1 counter on either Wildwood Scourge.
The Wildwood Scourge who didn't have the counter put on it triggers, putting a +1/+1 counter on itself.
Repeat step 3.

Combos with "Wildwood Scourge"