This came up on the Sunday event that I run. I was playing the Professor X & Magneto duo figure and successfully Mind Controlled my opponents Korvus. There where only three players so I was playing the bye rounds. He had already used his "Blade of the Phoenix" ability once so the indicator was down to "4." My opponent and I discussed it and agreed that for the "Mind Controlled Attack" the indicator would reset back to "5" for me as it was the first time for me to use it. The real question then became as I mind controlled him later in the game would the indicator once again "reset" or would the "Mind Controller" be down to a "4" for the second time they have Korvus use that power?

OR did the both of us over think it all and deal extra damage that should not have been dealt?

I am not a judge, but I would say the change of team loyalty has nothing to do with the counting of attacks resetting. He is attacking for the second time in the game, so his "blades" are set at 4.

I believe it should be reset for each new controller. Similar to "Once per game" powers/abilities, it is the first time for you to activate that power, regardless of whether it has been activated before.

Now, if you Mind Control him again later, the damage value would go down 1, as you (the controller) have actually used his power before.

This is true. Mind Control resets the power, so his damage will be 5.

Part of me seems to remember something about each instance of mind control resetting the power. But I'm not sure...

Each different mind controller resets "once per_____" effects. If you MC with Chuck&Mags and then later MC with them again it would count as the second use by that controller.

Thank you for the heads up Necrodog. That is how we played it. Just figured that I would drop a line here in the rules forums in case anybody else was just wondering.