Purely from a hunters perspective, I reckon as far as the big 5 are concerned, the most dangerous animal will be determined by the circumstances and terrain.
ie.. in the bush with poor visibility , a wounded Buffalo will take some beating.
In more open ground, with ground cover(grass and low bush) a wounded cat would be a front runner.
Elephant really surprised me in the thick stuff, couldn't see the buggers, even when we were close enough to hear their stomachs rumble.
All exciting stuff.
M.