In Cosmic Encounter (Eon edition), the Wrack's power is to offer a deal to the other player in an encounter, rather than fighting. If the opponent refuses, the Wrack "tortures" the opponent: for each token the Wrack has committed to the encounter, it may send one of its opponent's tokens or cards to the warp or discard pile, respectively.
It's not clear from the description on the power card itself, but the Wrack must follow through completely: the Super Flare allows the Wrack to stop the proposal/torture and go back to normal encounter resolution.
That lack of clarity makes me question two other things about the power:
1) Can the Wrack offer a deal (intentionally or not) that the opponent is incapable of accepting? A simple example would be "give me the Attack 40 and I'll give you a Compromise" where the opponent does not have the Attack 40. Further, if it's unknown whether the opponent can fulfill the deal, can they dodge the process by (truthfully) stating that they cannot fulfill it?
2) Can the Wrack change the deal? This would seem to be essential for the process, given the iterative way it's described:
On each torture you put any one of his tokens into the warp, or one of his cards (drawn at random) into the discard pile. If at any time he accepts the deal, stop the torture...
The opponent can clearly do whatever math is necessary before the Wrack starts removing anything (though it's true that which cards will be discarded is an unknown); combined with the fact that the Wrack can't stop without being Super, there's not much point in actually repeating the process as opposed to doing it all at once if the deal can't change on each step. However, the existence of the Super Flare makes me question that interpretation, because based on a straight reading of the power card:
If he refuses it you may torture him once for every token you have in the challenge.
(emphasis mine), it sounds like the Wrack is choosing at each step to perform the torture, and I would have thought that the ability to stop was built in.