This is the situtation came up while battling on Pojo Apprentice League

This is the situtation came up while battling on Pojo Apprentice League:

Say it's your turn and you use a Defender on a Tentacool (with 20 damage on it) to prevent it from getting knocked out.

Then your opponent decides to put 4 PlusPowers on his Mankey and uses scratch. Would my pokemon be knocked out? Or would defender block all the damage, since PlusPower uses the wording, "when damage is done"

After weakness and resistance is applied, then all non-Pokemon Power effects are applied. Defender is -20 and 4 Plus Powers would be +40. The two apply together for a net of +20. Add in 10 for Scratch and it will deal 30 damage, knocking out the Tentacool.

Scott