Re: Beating Dr. Destroyer...how do (or did) you do it?
Well, there's always this:
Please Mommy, Don't Hurt Me!: PRE Drain or Transfer, w/ penetrating (x2 if necessary), long-lasting perhaps.
I'd never allow this, because it totally breaks Dr. Destroyer's concept of being the most bad-ass villain of the modern age. I'd say he has a Dispel (or the like) in one of his bases, frex. He just has to work up the courage to use it.
That and the PC stupid enough to do will create of TPK (or worse, see below) of epic proportions. Here' the list I drew up, in increasing level of nastiiness:
1) Death From Above!:Orbital laser
2) BOOM!: Multi-megaton nuke
3) Human Extinction Attack!: Kill 90% of humanity (like in The Island of Doctor Destroyer module)
4) Dimensional Portal/Really Big Hyperspace Sign: Summon Azozoth (sp?)/Galactus-analogue or the like
5) The Cable Option: Go back in time, clone the offending character, switch the babies of the playing character PC is the clone, train and modifier the real character is a drooling, deformed "attack dog" who obeys all the Doctor's whims and attacks the PCs on a regular basis. The "attack dog" will, of course, be really hard to kill, but easly to splatter so the Doctor can beat him. Again and again and again.
Actually, #5 seems interesting, despite being like several Iron Age stories. (Which was not intentional, really. Except for Cable.)