Yep. Outsider it is, then.
Since it is "larger than a cave bear", which in 3e is a dire bear, then it is bigger than this:
A typical dire bear is 12 feet long and weighs as much as 8,000 pounds.
Increasing a leopard to Large yields the following stats:
Str 24, Dex 17, Con 19, Int 2, Wis 12, Cha 6
Full Attack: Bite (1d8+7) and 2 claws (1d4+3)
+3 natural armor
The bite damage obviously must be improved, and its mental stats need to be improved, since it is intelligent and uses spell-like abilities. Maybe...
Str 24, Dex 17, Con 19, Int 14, Wis 15, Cha 17?
AC translates to 22, so natural armor should probably be increased, and Dex could be increased if we want.