Kalamax, the Stormsire + Return the Favor Combo

Kalamax on the battlefield (Kalamax tapped on the battlefield).

Return the Favor in hand.

You have an additional castable sorcery.

plus the cost of the additional sorcery available

Cast any sorcery by paying its mana cost.

Holding priority, cast Return the Favor by paying its mana cost.

Kalamax's first and second abilities trigger.

Resolve the first ability, creating a copy of Return the Favor and choosing to copy the original Return the Favor.

Resolve the second ability, putting a +1/+1 counter on Kalamax.

Resolve the Return the Favor copy, creating a copy of Return the Favor.

Kalamax's second ability triggers, putting a +1/+1 counter on itself.

Repeat from step 6 any number of times.

Infinite +1/+1 counters on a creature

Infinite magecraft triggers