In the modern day, Rugby/Rugby League gets the edge. No pads and collision is required. Your flesh and bone is your padding.
But, I would say that American football and hockey are very close.
I'd argue that pre-2000s American football would have taken the cake due to increased lethality. You had psychos on banned supplements willing to hit anywhere.
Pre-2000s hockey is also up there in terms of physicality. Open-ice hits and fighting. If you dial it back more, you had helmet-less skaters and goalies
playing around with 100mph pucks and high sticks.
[ Edited by zonkers on Oct 8, 2015 at 2:04 PM ]