A Sumerian king.  There are no known images of Lugalzagesi.

Lugalzagesi came to power as the ensi (ruler) of Umma, a title he inherited from his father,
U-u. He was also the high priest of Nisaba, the patron goddess of the city. The current pronunciation of his name is Lugal-za-ge-si, with many alternative spellings, including Lugalzaggessi and Lugalzaggisi. The Sumerian signs for his name are shown below.

Lugalzagesi unified the Sumerians under his rule and conquered many foreign countries.
He called himself “the king of all nations.” “All those on thrones in Sumer and the rulers
of foreign lands” acknowledged him as their king. Lugalzagesi ruled for 25-34 years
(depending on which version of the King List is correct) in the mid 24th century B.C.
He was the last king of Sumer before it was conquered by Sargon and the Akkadians.

  Lugal-za3-ge-si

Lugalzagesi conquered the Sumerian cities of Ur, Larsa, Girsu, Lagash, and possibly others, and eventually brought all the other cities of Sumer under his control. Lugalzagesi is sometimes credited with being the first king to unite the numerous city-states of Sumer
into a single nation, but this distinction must really go to several earlier kings.
This in no way diminishes the accomplishments of Lugalzagesi. Each of the city-states
had a proud tradition of independence dating back through the centuries. They jealously guarded their autonomy and their own self-interests. They were often at war with each other.
In this way, Sumerian history resembles that of ancient Greece, where the rivalry and
independence of the city‑states prevented Greece from ever becoming more than the sum
of its parts.

Most efforts to unite the Sumerian city-states had ended in failure, and the periods of Sumerian unity had always been brief. After the death of the king who had unified them, the many city-states would once again go their own separate ways. Only a strong king like Lugalzagesi could unite the cities of Sumer, and it speaks well to his powers of kingship
that he was able to hold them together for as long as he did. It would be more than
200 years later, during the Neo-Sumerian Revival, at the very end of Sumerian history,
before Sumer once again became a unified nation.

  Lugalzagesi, ensi of Umma.

Lugalzagesi’s efforts at unification sometimes carried a heavy price. His war with Urukagina, the king of Lagash, was especially bitter (described on the "Urukagina" page). Lugalzagesi had to besiege Lagash, and the neighboring city of Girsu, three times before they finally fell. Once inside the cities, his soldiers sacked them with a ferocity that shocked the Sumerians. This kind of brutality was seldom seen in Sumerian warfare. They conducted their civil wars according to the rules of 'civilized' warfare, but Girsu and Lagash were treated like they were foreign cities. The plundering of the temples was particularly appalling to the Sumerians,
who were a very religious people. A tablet that was written after the fall of Lagash describes a litany of transgressions, “To the Antasura temple he set fire, and its silver and lapis lazuli he bundled off. The palace of Tirash he plundered, the Smaller Abzu he plundered, the dais
of Enlil and the dais of Utu he plundered. The Ahush he plundered, and its silver and
lapis lazuli he bundled off...” (The Man of Umma). The violent sacking of the city and the
sacrilegious looting of the temples has always condemned Lugalzagesi in the judgment
of history.
 

Without excusing his actions, a word must be said in his defense. First, according to the established rules of ancient warfare: the longer a city held out, the worse its fate when it finally fell. If a city surrendered quickly it could expect some leniency. On the other hand,
if a city resisted for a long time, costing the king more money and the lives of his men,
then the consequences were always much worse when the city was taken. For instance,
the medieval Europeans, who were much practiced in the art of siege warfare, developed
a precise timetable of escalating consequences for each stage of a city’s resistance;
ranging from fair and honorable treatment if the city surrendered quickly, to heavy fines and
indemnities, to the plundering of the civilian population, to sacking and burning the city
if it had resisted for too long. It must be remembered that Lugalzagesi had to besiege
Lagash and Girsu three times before he conquered them; so his soldiers, who had seen
many of their comrades killed in the attacks, were in no mood for mercy when they finally
broke through. Lugalzagesi himself would have considered the silver and lapis lazuli that he “bundled off” to be fair payment for his expenses. His harsh treatment of Lagash also had
a calculated psychological effect. It sent a clear message to the other Sumerian cities:
“This is what happens to cities that defend themselves too heroically,” thus inducing them
to a quick surrender.

It's possible that many of the Sumerian cities that Lugalzagesi allegedly "conquered"
gave up without a fight after they saw what happened to Lagash.

Second, there’s another reason why Lugalzagesi treated Lagash the way he did. Umma,
his native city, and Lagash had been at war for more than a century. They battled to control  the Guedena, the fertile plain that lay between the two cities. The original border had been demarcated by Mesalim, the king of Kish, who was called upon to settle the dispute. His ruling was favorable to Lagash, the larger and more powerful of the two cities. Steles were erected to mark their respective territories, but Umma had never been happy with the ruling. As a result, the army of Umma often marched across the border and “smashed to bits” the offending steles. A war inevitably followed, and Umma was inevitably defeated (with only two exceptions in the course of a hundred years). Then a heavy fine (in the form of an interest-bearing “loan” of grain) would be levied against Umma. In effect, Umma became a vassal city of Lagash. Umma often couldn't repay the loan or the accrued interest, so its army would again march across the border and re-smash the re-built steles. It was an impotent gesture; the army never occupied the territory for long. This would provoke another war; and so the cycle continued, for generations on end, and Umma always lost. One has to sympathize with Umma, which was always beaten down by the city of Lagash. It’s therefore not surprising that when Lugalzagesi got the chance he thoroughly sacked Lagash, thus avenging a century of humiliating defeats. There’s no evidence that Lugalzagesi treated the other cities this way, so it’s not indicative of the way he ruled his kingdom.

  King of Uruk.

At some point during his reign Lugalzagesi made Uruk his capital city. It’s often stated that he conquered the city, but this is unlikely. Lugalzagesi claimed he was "the servant raised by the goddess Ningirim, queen of Uruk,” suggesting he had a previous connection to the city, possibly during his childhood. It may have been the city where his mother was raised. Most likely he became the king of Uruk by marrying the daughter of the reigning monarch and thus gained the kingship by marriage rather than by conquest. Thereafter, 'King of Uruk'
became his chosen title rather than “Ensi of Umma.”

After settling matters in Sumer, Lugalzagesi turned his attention to foreign lands. He went on to conquer Akkad, Sumer’s neighbor to the northwest. In so doing, he became the “King of Kish,” the traditional title for any king who ruled all of Sumer and Akkad, although he is not named as such in any surviving documents. He also conquered Elam, Sumer’s neighbor to  the northeast. He later conquered parts of Syria. Lugalzagesi could therefore claim he ruled the world from the Upper Sea (the Mediterranean) to the Lower Sea (the Persian Gulf). It’s been suggested he didn’t actually rule these territories, but only successfully raided them. Maybe this is true; perhaps he was only just beginning to build an empire before his death. Things might have been different had he lived longer.

Lugalzagesi gives a pleasing portrait of life during his reign. “In those days, Uruk in rejoicing spent its days under him. Ur, like a bull, its head skyward did lift up under him.” He goes on
to list other cities, but fails to mention Lagash. Presumably, Lagash had little to celebrate
during his reign. Otherwise, “All the lands in river meadows rested (contentedly) under him,
and the nation was happily making merry under him.” (Lugalzagesi Translation). By this time
he was getting on in years. Assuming he came to power when he was 25 (just a guess)
he was now 50 - 59 years old, depending on how long he reigned, which is quite elderly
by the standards of the ancient world. He could rest content; things were going well, until...

  Sargon.

There was an insurrection in Akkad. A man named Sargon, a mere Cup Bearer, had overthrown his king, Ur-Zababa, in the city of Kish. Ur-Zababa had been a vassal king of Lugalzagesi. Sargon went on to unify (or conquer) the Akkadians, and was now leading an army toward Sumer. To meet the threat, Lugalzagesi gathered together his own army, the “army of fifty ensis.” This was either an unprecedented show of unity among the Sumerians or it demonstrated Lugalzagesi’s total control of the Sumerian city-states.

There were two pitched battles. The Sumerians were defeated both times. It's been
speculated that some of the ensis were less than enthusiastic in their defense of the realm,
or they abandoned the battlefield, or they even switched sides, believing that Lugalzagesi
was a greater threat to their independence than Sargon. If they truly believed this, they
could not have been more sorely mistaken. They were soon to be bitterly disillusioned.

The following section is from “Warfare in the Ancient Near East to 1600 BC: Holy Warriors at the Dawn of History,” by William James Hamblin. It begins with a Babylonian inscription:

“Sargon, king of Akkad, steward of the goddess Ishtar, king of the world, anointed priest of the god Anum, lord of the land, governor on earth for the god Enlil, was victorious over Uruk in battle, conquered fifty governors with the mace of the god Ilaba, as well as the city of Uruk and destroyed [Uruk’s] walls. Further, he captured Lugalzagesi, the king of Uruk, in battle and led him off to the gate of the god Enlil in a neck stock.”

Following his victory over Uruk, Sargon faced a new challenge. The Sumerian vassal rulers had asserted their independence after the fall of their overlord Lugalzagesi to Sargon, requiring him to undertake at least four additional campaigns in Sumer to secure Lugalzagesi’s entire former domain.

“Sargon, king of Akkad, was victorious over Ur in battle, conquered the city and destroyed its walls. He conquered Eninmar, destroyed its walls, and conquered its districts and Lagash as far as the sea [Persian Gulf]. He washed his weapons in the sea. He was victorious over Umma in battle, conquered the city, and destroyed its walls.”

The important after-battle ritual washing of weapons was designed to cleanse them of blood and purify them. When inscriptions describe Sargon’s weapons being washed “in the Upper and Lower Seas” (the Mediterranean and Persian Gulf), it is meant to indicate that Sargon had reached the end of the known world, and could therefore ritually cleanse his weapons, since there was nothing left to conquer. [It is probably also a direct allusion to Lugalzagesi’s claim of having conquered the entire world from the Upper to the Lower Seas. jjs]

The destruction of the walls of a conquered city, while not unknown before, became
standard policy under Sargon. Presumably the city walls were not entirely destroyed,
but were left with major breaches or without gates, rendering them indefensible and thereby making rebellion a very dubious proposition. The fact that so many cities in the Akkadian empire repeatedly rebelled despite their ruined city walls is an indicator of the great hatred
the conquered people had for their Akkadian overlords.

[The Akkadian Empire was truly despised. When it finally fell, its capital city of Agade was
so thoroughly destroyed that no one today even knows where it is.  jjs]

The aged Lugalzagesi was dragged to Nippur in a neck stock and marched through the city in Sargon’s victory procession. As a final humiliation, Sargon made him watch the construction of a victory stele commemorating his defeat. It must have been agonizing for Lugalzagesi, watching the stele take shape, knowing that when it was finished he would be executed.

It is easy to imagine how the final scene unfolded:  

When the stele was at last completed, Lugalzagesi was hauled from his prison cell and paraded through the city streets, to the howls and derision of the people. Perhaps now, after months of humiliation and mistreatment, he welcomed the end. He was taken to the
temple of the war god as the place for his execution, which was the custom of Akkadian kings. In front of the temple stood the newly erected victory stele, surrounded by priests and dignitaries. After a boastful speech by Sargon, Lugalzagesi was dragged to the base of the stele and forced to the ground. Then with proper pomp and religious ceremony, Lugalzagesi was put to death. It was an inglorious end to a great Sumerian king.

It would be more than two hundred years later, at the time of Ur-Namma, before Sumer would once again be ruled by a Sumerian king.

  Lugalzagesi