The Binding of Isaac: Rebirth as The Lost. It's a whole lot easier in Afterbirth as you can get Holy Mantle as a starting item. But without that it's insanely hard. And you have to do it at least three times to get dat platinum trophy, Pure madness I tell you! But I did it. I died at least 1,000 times while trying, but I did it. =P
Official member of VGC's Nintendo family, approved by the one and only RolStoppable. I feel honored.