Did you know that in Jesus' time, there was no concept of hell as we came to know it thanks to Dante? Some Jews of the time held no belief in the afterlife. Jesus did. And those who did believe, also believed in a time of purification after death for those who had been less than they should have been. Undoubtedly, this was unpleasant. Jesus often compared it to Gehenna (the city dump) where the fire never went out and the trash was burned away. It was compared to gold being purified in fire.
Yes, Jesus also mentioned the reality that a soul that was truly evil was likely to be destroyed by God. Here we come back to the light vs darkness analogy. Just as darkness cannot exist where there is light, evil cannot exist where there is true goodness. Likewise, goodness does not destroy what is good any more than sunlight destroys light from a bulb or candle.
Keep in mind, we do have the ability to reason up to a certain point. God is pure love and evil cannot exist where there is love. To be fully with God, any evil must be burned away. The good remains. What remains a mystery is, "What will that be like?"