Rabbi Yosi the Gallilean said: The Egyptians were struck by ten plagues in Egypt, and fifty plagues at the sea…
Rabbi Eliezer said: …In Egypt they were struck by forty plagues, and at the sea by two hundred plagues.
Rabbi Akiva said: …In Egypt they were struck by fifty plagues, and at the sea by two hundred and fifty plagues.
This is the most obscure passage in the Hagada. The rabbis culled our vast body of teachings and created a script for families to recite year after year to recall our story, bolster our faith, bind us as a people, and transmit our precious tradition to the next generation. But what did they expect us to learn from this esoteric debate that seems divorced from reality.
There are two issues. The first is figuring out what these plagues actually were that struck the Egyptians at the sea. The ten plagues in Egypt were so noteworthy that the Torah spends reams of precious words extolling them. Now the rabbis inform us that those plagues were trivial compared to the barrage at the sea. Yet the Torah does not mention this second assault at all. Not a word. The second issue is the numerics. All three rabbis agree that the plagues at the sea were five times worse than the ones by land. Their debate concerns how many plagues there were in total—50, 200, or 250. What is the significance of these numbers?
I’m going to explore the first question at length and address the second more briefly.
The ten plagues began in the month of Tamuz. Each plague lasted a month—one week of warning, three weeks of plague (or vice versa, by other opinions).  After the third plague (by Rosh HaShana) the Egyptians were so debilitated that their enslavement of the Israelites terminated.  Each subsequent plague broke them still more. By the end they were on the verge of total collapse.  As the archetype of evil in those days, if Egypt went, evil would cease, free choice would collapse and the purpose of creation would be lost. Contrary to popular belief, the critical timing of our exodus (its hasty execution called chipazon) was actually to salvage evil.  HaShem backed off at the last minute, so that a remnant of evil could survive, recover and (seemingly) even prosper. Creation requires its contribution though it is our job to seek its demise. (That last statement is paradoxical but not contradictory). 
And the tenth plague, the death of the firstborns, was so devastating to the Egyptians that their cry that night (reports the Torah) was more agonizing than any other cry that ever was or will be. 
Conversely, at the sea, Pharoah’s army comprised 600 chariots (carrying, say, two or three soldiers each).  The total number of Egyptians that drowned there was (at most) 1,800. Not to minimize the value of a single life, or the heartbreak of those who mourn them, but that loss does not approach the devastation wrought by the ten plagues (especially the death of the firstborns). Besides, they were soldiers and that is the way (and the risk) of war. It is a natural (if dreaded) loss.
So on what basis do the rabbis claim that the plagues at the sea were five-fold more severe than the previous (famous) ten. Where is their evidence for this contention?
Some bring midrashim that whatever could go wrong for the pursuing Egyptians did go wrong. The pillar of cloud that led the Israelites by day, produced darkness for them and caused the ground under their feet to be soft as clay. The pillar of fire by night singed them and melted the wheels of their chariots. Their horses got stuck in the mud, the soldiers fell off, and could not remount so when the waters returned they could not escape. Some died quickly, some slowly, depending upon their state of demerit. These adversities hardly compare to the drama and devastation of the previous ten plagues (neither quantitatively nor qualitatively).
Perhaps the key lies in the difference between physical travail and ego death. The former is awful, incapacitating and sometimes even tragic. The latter (as used here) is a tsunami of shame and self-revulsion that drowns out all trace of self-worth. These two ordeals are not mutually exclusive…in fact they often overlap: Physical travail often produces shame; ego-death often leaves illness and devastation in its wake. Yet a distinction can be made. Physical travail, may turn a life upside down, it may ravage quality of life but (in and of itself) it does not touch core (except indirectly, via the ego death that it sometimes triggers). Conversely ego death does cut to the core which makes it the greater trauma (at least qualitatively).
People have various susceptibilities to ego death. Some people melt down into rage, envy, shame and humiliation by the slightest snub. Others endure public insults and tribulations without losing their dignity or integrity.
There is evidence to associate physical travail with the original plagues and to ascribe ego death to the events by the sea. The Hagada informs us that the extraction of the Israelites from the midst of their Egyptian hosts via the Ten Plagues was executed by the Blessed Holy One and His Shekhina.
HaShem brought us out – not through an angel, not through a seraph and not through a messenger. It was the Blessed Holy One alone, in His glory…
[He brought us out] with great fear (ובמורא גדול) – this is the revelation of the Shekhina. 
The Blessed Holy One and His Shekhina associate with the final two letters of HaShem’s name (the vav and the hei). They mediate the lower aspects of Divine providence, the hashgakha of reward and punishment where justice rules and every action always brings consequences (for good or bad as the case may be). If this were the only providence we would rise and fall eternally. In one lifetime we’d fix some things but damage others. In the next life we’d repair those but slip in something else. And so it would go, up and down, round and round for eternity.
In this lower providence that revolves around cause and effect everything is possible. If at first you don’t succeed, then practice harder, improve your deeds. If you lose the battle, you can still win the war. Pharoah had a stiff neck.  He believed that if he found the right magicians, bargained hard, or just refused to budge, that he could lick Moshe’s god. He had never encountered an adversary that he could not dominate. Pharoah interpreted the plagues as a physical travail. There were moments when he started to crack but he always recovered and never let the plagues undermine his abiding sense of personal power. Only at the very end with the horrendous plague of the firstborns did Pharoah admit defeat. But even then, as soon as the Israelites doubled back, and there was reason to suspect that their mighty G-d had met His match, Pharoah pursued, believing that victory was still within his grasp.
Conversely, the level of Divine providence that parted the sea was Atika, associated with the highest tip of the first letter of HaShem’s name (the yud). This Higher Providence called (Mazal Elyon) holds a vision of the purpose of creation and ensures that every moment, without exception, brings us closer to it. Mazal Elyon includes all the things that are fated in our lives (both individually and collectively). The Zohar tells us that at the water’s edge, Atika shone for all to see.  At that point Pharoah’s soul must have realized that all was lost…for eternity. That these Israelites and their G-d were going to change the universe. That their worldview of ethical monotheism was going to rule. That he and his people had no choice but to assimilate into their mission (and on their terms). That he was a humble servant of the Holy One, just like everyone else. That his whole life—all that he accomplished with his stiff neck and ego strength—would count as a debit in the Holy One’s chronicles. Now that is a massive ego death.
And it actually accomplished what the ten plagues could not. The midrash says that Pharoah was subsequently appointed king of Nineva by the angel Gabriel. When Jonah preached fire and brimstone upon that metropolis for its grave sins, Pharoah got the whole community to repent, and managed to reverse the decree.  Pharoah did his teshuva.
This next section, analyzing the number of plagues, is addressed to those familiar with the vocabulary of the Ari. The material is not unpacked, for time is short and Pesach draws near. It is possible to skip this discussion and go to the last two paragraphs—a summary and final blessing.
The question underlying the rabbis’ debate about the number of plagues is how deep did the lessons at the seashore sink in. A king like Pharoah is a hub-soul with spokes connecting to every one of his subjects. Whatever happens to a king affects his entire people. And then, on top of that, Pharaoh and Egypt are archetypes. They represent the ego layer of our universe-encompassing Adam. Whatever changes they go through affect the entire course of human history. Israel, too, is an archetype and represents this Adam’s neshama layer as it comes of age and contests the ego’s repressive regime. The neshama’s goal is not to liquidate the ego but to subdue it, enlighten it, and eventually incorporate its valued perspective into the steering committee. 
The whole point of the plagues was to burn into the ego’s nerve net the experiential knowing that crime doesn’t pay—that resisting spiritual law always hurts more than it gains. The more deeply the lesson absorbs at this archetypal level, the easier it becomes for subsequent generations to get that message as it gets transmitted through the providence of their individual lives.
Just as light is comprised of small packets of energy called quanta, so is this true for consciousness, teaches the Ari. Its quantum units are called nekudot. And these nekudot evolve into sefirot and eventually into partzufim. They are kabbbalistic milestones in the evolution of consciousness.
Nekudot = dark knots of unactualized potential that are the debris of shevirat hakaylim. These dense slivers of dark light gradually rise to the “surface” and incarnate as a creature, object or moment of our world. At that point they they unfurl into sefirot.
Sefira = the irreducible unit of ten nekudot arranged along three pillars also called the Tree of Life. This is the basic atom of our holographic world where every piece contains aspects of other piece within it. Every sefira always contains ten interincluded sefirot (or nekudot), which also each contain ten, ad infinitum. Each sefira is a single attribute of personality.
Partzuf = these ten sefirot unpack, elaborate and reorganize into five partzufim (of ten sefirot each). A partzuf is an archetypal personage that mirrors the psychic complexities of a human being (more than a sefira is able to do). These five partzufim comprise a family system where each plays a different role (grandparent, father, mother, son, daughter). They also (often) function as different voices or sub personalities within a single individual.
An accompanying diagram illustrates this following table.
PLAGUES BY LAND
50 plagues at the Sea = these ten sefirot unpacking, elaborating and reorganizing into a single partzuf with its five interincluded parzufim, including the crown.
200 plagues at the Sea = this single partzuf unpacking, elaborating and reorganizing into a full system of partzufim, except not including the crown. The core (on the level of partzufim) is not touched.
250 plagues at the Sea = this partzuf unpacking, elaborating and reorganizing into a full system of partzufim, including the crown, or highest partzuf call Arikh Anpin. The core is touched on all layers.
How deep did the lessons of the plagues absorb into the nerve net of the Egyptians and bring tikun there? The higher the number the more deeply the plague penetrated into the body, mind and soul of Pharoah. Rebbe Akiva believes they touched core, R. Yossi is more cynical and considers their impact to have been superficial.
Let it be that at our holy sedar, when the lights of Higher Providence stream down, that the Pharoahs of the world—both inside us and without—should, like their ancient forebear, also see the light. May they take it in, and take it to heart, that the Almighty is an unstoppable force that will free the world from all tyrannies. Then and there, may they admit defeat, lay down arms and reorient toward truth. May the transformation wrought by this turning remove all stops and bring Mashiach, NOW.