Let's begin by stating that, whether you know it or not, Quasi-Existentialist philosopher Martin Heidegger and his Destruktion mark what can be seen as the end of philosophy with two shifts in subject.
First is the end of philosophy as metaphysics. Heidegger took from Hegel an anti-metaphysical bent, however indebted he may be to Aristotle. Hegel wrote about philosophy with an emphasis on dialectical shifts in level, proceeding from the authors' conscience (or Derrida's notion of 'Authorship') to the primordial page via the movement of Geist.
While Heidegger avoids dialectic, his emphasis remains purely in the spirit of Holderlin- with a fair amount of attention paid to ingenuity and getting around tradition. He famously said, "Every attempt to circumvent traditional concepts in philosophy is met again by tradition.".
So there is a sense in which Heidegger can be seen as the great butcher of philosophy, begetting deconstruction while attacking the pillars of traditional metaphysics. In Heidegger's repudiation of Husserlian 'method' and turning away from ancient metaphysics he instinctually put emphasis on questions of heuristics and phenomenology in a non-intentional sense. Husserls retreat to 'method' (ie the phenomenological method, eidetic method, and intentional analysis), and his subsequent denial of the profound instinct to view philosophy as science, relegated philosophy to a place worse than death. If Heidegger could be seen as the butcher of philosophy- Husserl (to whom Heidegger dedicated Being and Time) could easily be looked upon as the kernel of the transformation of existentialism to Sartre's confused seminal Being and Nothingness. In an attempt to synthesize Husserl with Heidegger, Sartre created his eidetic intuition concept. This is in stark contrast to Heidegger's 'Primordial Intentionality', so much so that the very notion of eidetic intuition can be seen as a misunderstanding of Heidegger- only in that it takes his 'primordiality' concept and blends it with Husserlian method, which leads to a confusion between emphasis of subject. As Robert Denoon Cummings says in his 'Phenomenology', The method becomes the subject-in-itself- which is a different subject than primordial intentionality, or 'engaged-coping-with-the-world'. When these subjects are conflated, it leads to the kind of confused word salad of Being and Nothingness.
Sartre of course almost exclusively read Husserl in the pre-war years, and always took with him a Cartesian sensibility in his phenomeno-existential pursuits- which lends itself to a conflagration of ideas by Descarte's very notion of Cogitare.
The second shift is the death of philosophy as science.
This was entombed by Husserl in his 'Crisis of the European Sciences' when he wrote famously "The dream is over". Heidegger knew instinctually that the age of philosophy as related to astronomy and geometry were dead and gone, and great writers like Geothe and Holderlin were more akin the the true flame of philosophy than the application of philosophy in the sciences.
What we needed was to understand what it means to 'be', and that means phenomenology (or the turning of consciousness back in on itself), existentialism (with it's emphasis on responsibility), or the understanding of philosophy as pure action.
I shall expound more on the 'end-of-philosophy' in future posts.
That's all for now dear reader~