I've given this a lot of thought, and while I can think of several ways to do it, most require some sort of specialized build. This means that you'd have to have the foresight that your character is going to encounter an energy drainer, and then probably also know that the GM is going to give the other guy a feedback limitation as well. That's a set of circumstances so rare that I doubt it has ever actually come up in a game before, anywhere ever.
So you either have a player and a GM plan out a specialized build for use in some future game session, or you have one person plan it all out on their own. That means either a player with a lot of points to blow on a very situational power, or a GM who gives a villain a bunch of odd limitations just because he wants to see a certain effect in play. The only other possibility is some sort of house rule that can be put into play without any sort of point expenditure, that hopefully has an easy to understand game mechanic behind it.
I think we've got maybe two optional rules that can come together to give us what we're looking for.
The first comes from the Ultimate Energy Projector, page 197 "Contests of Power". Normally this represents two blasters who shoot each others' beams and "wrestle" back and forth until one blast overwhelms the other. I'd suggest using the Drain/Transfer versus the defender's highest attack power to simulate this. Because Drains and Transfers are more expensive per die, I'd double or triple the Body scored by them when compared to a stat like Strength. A 6D6 Drain is 60 points, it should have an equal chance against a 60 Str character.
Because each character is willfully dropping any resistance to the other side, I would treat both attacks as basically NND. The defender against the Drain doesn't get any Power Defense (he's willingly dropping it so the other side can take as much as possible), and likewise the Drainer won't get any Physical Defense against the Str of the Drainee (if he does not win the contest of power). This is a last-ditch maneuver for each side to try to take the other out.
Since Power Defense is much more rare than Physical Defense or Energy Defense (and so the penalty of giving it up is much less than giving up PD/ED), and because Drains and Transfers are already rolling fewer D6s, I might declare that the Drainer is considered to roll maximum damage. So your 4D6 Drain automatically gives you a result of 24 points and 8 "Body" (the Drainee is "forcing" his power into the Drainer). The loser of the contest takes the full effect of the other side's attack, the winner takes no damage (but gets the effects of the Transfer if the winner is the Drainer).
The second optional rule that I would consider adding in would be an extended push. In a situation like this, characters are trying to go past their limits. You may allow them to make Ego rolls to push their powers by more than 10 points. This higher amount would be used as normal in the Contest of Power.
So, as an example, let's go with Captain Brick and Power Thief. Captain Brick has a 60 Str. Power Thief has a 4D6 Transfer vs any single superpower (+1/4). Power Thief uses his power on Captain Brick and rolls a 15. Captain Brick's Str goes from a 60 to a 45. A turn of terrible to-hit rolls passes and Captain Brick gains 5 points back, putting him at a 50. The good Captain realizes that Power Thief is going to slowly whittle him down, and he needs to end this now. Captain Brick holds his action, waiting for Power Thief to strike. Power Thief hits him with his Transfer. Captain Brick responds by shouting "You want my power? Take it! Take it all!" They then begin the Contest of Power.
Power Thief is happy to enter into this. He has a 4D6 Transfer, which as a 15 points-per-die power, means he gets a x3 Body score. He also gets to max it out because Captain Brick is willfully force-feeding him. So he counts as rolling 24 points and 12 "Body" for the contest. Captain Brick has 10D6 to roll. The Captain now realizes that he's got to roll really well to beat that 12 Body and win the contest. So he decides to push as much as he can. Power Thief sees that the Captain is going to attempt an extended push, so he decides he will have to do the same.
Captain Brick has a 15 Ego. Power Thief has a 10. The GM rules that for every 1 point they make the Ego roll by, the character can add an extra 5 character points for the push. Captain Brick rolls a 9. He made his Ego roll by 3 and so can push for base 10 + 15 more. He will roll 15D6 for his contest. Power Thief rolls a 10. He may push by an additional 5 points. He can add 10+5 to his Transfer (the GM allows this to go direct to the dice, without pro-rating for the Expanded Effect Advantage of +1/4). Power Thief now has 5D6 of Transfer, and because he maxes it out, he gets 15 Body and 30 Effect. This will go one of three ways:
1) Captain Brick rolls 15 Body, matching Power Thief. They are tied, no one wins, the fight continues into the next phase. Endurance is spent, new Ego rolls will have to be made, etc.
2) Captain Brick rolls 14 Body or less. Power Thief wins. Captain Brick loses 30 Strength from his 50, dropping him immediately to a 20. Power Thief adds 30 Str to his own Str score. Honestly, this might be too nice to Captain Brick given the seriousness of the maneuver, and perhaps the effect on the dice should be given a multiplier to make it even more devastating. It's supposed to be an all-or-nothing thing, after all.
3) Captain Brick rolls 16+ Body, and we'll say 50 Stun is rolled. Captain Brick wins. Power Thief immediately takes 50 Stun with no defenses allowed. This is enough so that he is at least Stunned, and probably unconscious. Captain Brick loses no Strength, but he is down a lot of Endurance.
There you go, that's my quick-and-dirty version of the classic comic book scene. Modify to your pleasure.