would probe them a bit on the "wonderful news" about God's Kingdom. Ask them who would be annihilated to achieve this. We know that the Society teaches that everyone who isn't a JW ( and even some who are but are weak ) will be destroyed including new born babies and children.
Yes once I establish non Jehovah’s witnesses will not survive, I always say that no matter when Jehovah chooses to execute Armageddon there will always be a certain percentage of unborn children, or very young babies, probably in their millions, that will die. If they claim that Jehovah knows the heart you can say that they must believe in predestination. If they attempt to blame the non believing parents and/or the State, you can say “didn’t Jehovah say no one can pay for the sins of another or a child it’s parents sins?”
I also like to ask if they believe in the soul. When they state they don’t I would ask what will happen to those who die of covid19 before Armageddon. When they say resurrection I would explain that due to decomposition, if you don’t believe in a soul, the resurrected person would just be a clone of the original person. Even more so if god wipes out bad memories as many witnesses believe. New body and new memories, how is that the original person in any shape or form? (Maybe send them a scan of the Wiki of The ship of Theseus).