I actually think worse-case is the better usage when describing all possible outcomes.
One could say "The worst-case scenario is that we don't meet sales projections"
But that can easily be topped by "Actually, the worst-case scenario is that we don't meet sales projections and we all get fired."
You can easily see how its not really possible to define a "worst-case" scenario from all possible outcomes as the list of negative effects can continue to grow.
Now if you are picking from a limited set of scenarios then I would agree that worst-case outcome is feasible.