I always thought "survival of the fittest" was probably a mistaken notion, since "survival of the fit enough" seems more than adequate to explain a lot of species' survival. I also think the whole notion of "fittest" has been misunderstood. It seems obvious from looking at many species that it is not necessary to be the strongest and most aggressive to survive. Sometimes it's the sneakiest, most agile, best at camouflage, fastest reproducers, most patient, etc. A lesson we can all learn from in bad times. But that's really a tangent, isn't it?
It almost sounds to me as if you are depressed that without a punitive god, the wicked prevail. But a lot of wicked people actually DO believe in a punitive god, and they are still wicked. If we could find an even better reason why people should be good, the wicked still wouldn't respect it. What can we do but think of them like bad weather, and try not to take it personally?