Oh man the full attack for the lion is deadly dude: 2 claws +7 melee (1d4+5) and bite +2 melee (1d8+2). Plus if he gets a bite on you he can pretty much not let you go.
Ya, basically what you have here is a really nasty rouge. I would put it at the equivalent of a multi-classed level 1 rouge / level 3 fighter. If you want to fight a Lion and live do what Kntoran said. Other than that get up in a tree, Lion's are not the greatest climbers and it may give you enough of an upper-hand to survive the encounter, if your lucky.
If your fighting a Lion solo, might as well say your prayers and hope for the best. However I want to point out the Lion must charge to use its best attack. If your character has a long spear or something it can set vrs a charge do that.