RE: ???
Placing damage counters is an effect of an attack. Remember that damage an attack does is always on the right of the card. So let's say that, for our example, Pure Power reads like this:
[C] [C] Pure Power (30)
Place 2 damage counters on the Defending Pokemon.
The attack has damage and an effect. The attack's damage is 30, and you factor in weakness, resistance, and any other effects that would alter attack DAMAGE first. Then you add the effect of the attack on, which places 2 additional damage counters on the Defending Pokemon. You don't count weakness or resistance for this part, nor do you factor in DAMAGE REDUCING effects either.
Now, let's say the Defending Pokemon is Metal and has 2 Metal energy on it, reducing damage by 20. So our Pure Power would do 10 damage to it, assuming weakness and resistance are null. Then, you do the attack's effect by placing 2 damage counters on the Defending Pokemon.
If the Defending Pokemon has an effect that says something along the lines of "prevent all effects of attacks, excluding damage, done to...." on it, then the attack damage would still go through, but the additional effect of placing 2 damage counters on the Defending Pokemon would not.
So in short, placing damage counters is an effect of an attack, not part of the attack's damage.
And sorry if my example sounds confusing. It sounded good to me when I typed it, lol.