Transformation through realization a.k.a enlightenment is a recurring theme in eastern philosophy. Is there a counterpart for this in Western Philosophical writings?
"Transformation of self" and "transformation through realization" are both pretty opaque statements. There's definitely themes of "transformation" (e.g. Plato), "enlightenment" (e.g. Kant), "progress" (Hegel, Marx), "authenticity" (Kierkegaard, Heidegger), wonder (e.g., Plato, Aristotle, Aquinas), and other things through the philosophical corpus.
If your specific question is about the self, then there's a lot on the evolution of the idea of the self in Hegel's Phenomenology, Sartre's Being and Nothingness, Anti-Climacus's [Kierkegaard's] Sickness unto Death and Taylor's Sources of the Self.
If you mean specifically the religious-spiritual mode in which that occurs in some eastern thought, there are similar traditions about self-knowledge before God in the Christian mystics and some Western philosophers.
Like many philosophical concepts, one need look no further than Plato. The Delphic maxim γνῶθι σεαυτόν or "know thyself" is oft used by his protagonist, Socrates.
The phrase you are looking for is the "beatific vision". It is the idea that our perceptions of beauty, truth and goodness in this world are a glimpse into a deeper reality which is accessed through the soul and self knowledge.
The first occurrence I know of is in Plato's Republic, which explains how seeing the Forms frees a person from slavery and teaches them who they really are, and uses the city as an image of the soul in order to understand a correctly ordered soul.
This theme is picked up by Christian philosopher theologians such as Boethius, Augustine, Justin Martyr, Bonaventure and Aquinas. It is also a standard hermeneutic principle during the Middle Ages, where the deepest meaning of religious scripture is how the soul achieves the beatific vision. In fact, it is the defining pursuit of philosophy and theology during this time.
The best popular expression of this idea is the Divine Comedy by Dante, which is a story about the escape of the soul from a false understanding of self to achieving the beatific vision.
Yes, there is. Heraclitus, Socrates, Jesus, and Spinoza achieved it, even tho they didn't know the term, as had millions of humans who lived before the nuclear family apocalypse 3000 years ago. It is universal, Upanishads, for example, are all about it.
And it is the real enlightenment -- the opposite of its "ego death" fake. Your Ego is your Self, your human soul. "Ego death" is when your soul, your humanity dies. What is left is the animal mind, what we inherited as-is from our, well, animal ancestors. Pets are happy bc they are born, live, and die "enlightened". "Ego death" brings a person closer to the happy state of animals, but the latter are still ahead because they are incapable of suffering and they will never know death.
The real enlightenment achieved by fully developing your humanity, by letting your soul flourish. In scientific terms, it means acquiring a fully rational system of beliefs. For starters you must be your rational conscious Self -- you must think for yourself. Most people live as their egos, and it's impossible to convince any one of them to try and become Self.
The Self can actually think in terms of mental models -- 3-D models of some aspects of reality. Individual models can be pieced together like a jigsaw puzzle (also "connecting the dots") into a more comprehensive simulation. Fitting each piece, connecting models makes a eureka moment, the proverbial light bulb going off in your head. When you reach a critical mass, there will be a moment when everything falls in its places and your whole world lights up -- that's enlightenment. Before that moment you were wandering through your life like through a dense forest with your eyes closed. Enlightenment opens your eyes. It liberates you in general -- to see where you are going, to know what you are doing. And liberates you from fear. Only when you are not scared of death anymore you will not be afraid to live your life.