There's no answer that will satisfy an atheist.
Some points I like to raise are:
1. Love does not mean always making someone feel good. If a child is eating chocolate every day and their teeth are rotting you are going to take away their chocolate and make them go to the dentist even if they are crying and distraught about it. Just letting their teeth rot and allowing them to get diabetes because eating chocolate makes them feel good would be a complete and abject failure when it comes to loving them. Love entails at times making your beloved suffer in order to achieve a greater good.
2. Atheists will ignore things being made right in the afterlife. So their version of the problem of evil is not an internal critique, its a semi-internal critique. They will assume God when they say "why would God allow a child to get cancer and die?" But then they act like an atheist when they assume getting cancer and dying is a pointlessly intense period of pain followed by senseless oblivion. Whereas the actual view they should contend with is that this was allowed for the salvation of the entire family and dying from cancer is a small price to pay for an eternity in paradise.
3. Ultimately the problem of evil is arrogant because it suggests that things could or should be ordered differently. So it could be rendered as "if God why am I not God?" Because thats what it boils down to. Why doesn't God order things how I want? Why doesn't He do it this way? If I was God I would do it like this... its just pride at the base of it.
