Hi can you exhaust a card when it is not your turn like the Retribution card which says exhaust this card after a monster within 2 spaces of you resolves an attack that affects another hero. That monster suffers 2 wounds so can you exhaust the card on the monsters activation turn or any other heroes turn?

Yes. The timing is as stated on the card - immediately after a monster within 2 spaces of you resolves an attack that affects another hero.

You may exhaust a card whenever the timing conditions are met - if the timing is not defined on the card (as with your other question about Stalker) then it has to be on your turn.