Gravitic Punch + Kalamax, the Stormsire + Return the Favor

Gravitic Punch

Kalamax, the Stormsire

Return the Favor

How it works

1. Cast Gravitic Punch by paying its mana cost, targeting Kalamax.
2. Holding priority, cast Return the Favor by paying plus an additional 1 to select its first mode, targeting Gravitic Punch.
3. Kalamax's first and second abilities trigger.
4. Resolve the first ability, creating a copy of Return the Favor targeting the original Return the Favor.
5. Resolve the second ability, putting a +1/+1 counter on Kalamax.
6. Resolve the Return the Favor copy, creating a copy of Return the Favor, targeting the original Return the Favor.
7. Kalamax's second ability triggers, putting a +1/+1 counter on itself.
8. Repeat from step 6 any number of times.
9. Once you have an arbitrarily large Kalamax, have the final Return the Favor copy target Gravitic Punch. This'll create two copies of Gravitic Punch in addition to the original Gravitic Punch.
10. Resolve all Gravitic Punches, dealing infinite damage to each of up to three opponents.