Listen to them and you will maybe understand
I'm familiar with Liszt's sonata and ballades, and listening to them won't make me understand precisely what you mean by "powerful." The word does not, after all, have a universal meaning as applied to music, so any piece of music could be perceived as
powerful by somebody in some regard.
Liszt wrote a multitude of piano works, after all, and there's no basis for making a recommendation from among them unless you can specify the characteristics you're seeking, .