What's unique about beethoven's pathetique sonata?

The Pathetique was groundbreaking in many respects. From a structural point of view, it was practically unprecedented for a piano sonata to have a slow introduction, particularly of that length. It conjures up suggestions of what Beethoven's improvisations might have been like. Also, the tragic emotional realm of the work (Pathetique corresponding to "pathos") was without rival at the time in the piano sonata repertoire. If one were to draw a comparison to Mozart's a minor Sonata, k. 310, one can see how far the Pathetique has taken music. K. 310 is Mozart's most emotionally turbulent piano sonata, but Beethoven's Pathetique introduces not only great tragedy, but a certain violence (think of the jarring dynamic contrasts in the slow introduction) that he would further develop in works like the Moonlight and Appionata. While Beethoven's sonatas up to this point were undeniably dramatic and fit for the concert stage, in the Pathetique, Beethoven puts the piano sonata in a new light as an individualistic, romantic vehicle for self-expression beyond what had been done prior.