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If you choose the second mode for Heartless Act, you choose which counters to remove from the creature, no matter who controls the creature. You may choose counters of different kinds.
If you choose the first mode and the creature gains a counter in response, you can't remove counters from it instead; the spell just doesn't resolve. Similarly, if you choose the second mode and the creature loses its counters in response, you can't destroy it instead.
If you choose the second mode for Heartless Act, you choose which counters to remove from the creature, no matter who controls the creature. You may choose counters of different kinds.
If you choose the first mode and the creature gains a counter in response, you can't remove counters from it instead; the spell just doesn't resolve. Similarly, if you choose the second mode and the creature loses its counters in response, you can't destroy it instead.
