The sun obviously. Doesn't matter how many lions there are, they will be completely melted before they can even get close to the sun.
All of the lions would burn up as they approach the sun and they have no way of attacking it from a distance. Even if they were somehow immune to the heat and radiation, they still wouldn't actually be able to do anything to it.
I wonder if all the lions formed a ball, how many would it take to serve as an effective heat shield? :wippyeet:
There's plenty of lions, so as long as they attack at night, when they can catch the sun napping, the lions are nearly certain to win.