In the circuses of Ancient Rome, exotic beasts were commonly pitted against each other. The contest of the Asiatic Lions, the smaller version of the African Lion, against the tiger was a classic pairing and the betting usually favoured the tiger. A mosaic in the House of the Faun in Pompeii shows a fight between a lion and a tiger. At the end of the 19th century, the Gaekwad of Baroda arranged a fight between a lion and tiger before an audience of thousands. The Gaekwad favoured the lion, and as a result had to pay 37,000 rupees as the lion was mauled by the tiger.http://en.wikipedia.org/wiki/Tiger_versus_lion
I'd have to go with polar bears as the baddest land animal.