The Seven Kingdoms in HBO's Game Of Thrones featured a plethora of powerful monarchs throughout the seasons. Season 1 begins with Westeros united under Baratheon rule, and the surviving Targaryens banished to Essos. King Robert's death causes the country to splinter, with several different claimants donning crowns of their own.
Some rulers were more underwhelming than others, whereas others seemed strong and unstoppable. Many contenders warred for the Iron Throne, but which monarch was the most powerful? For this list, only sovereign kings and queens will apply, so monarchs made through marriage (e.g Margaery Tyrell, Selyse Baratheon, etc.) don't count.
Balon Greyjoy
In Season 2, Balon Greyjoy crowned himself King of the Iron Islands for the second time in his life. The Ironborn monarch rebuffs Robb's peace terms before ordering an assault on the North.
To his credit, Balon was the last of the Five Kings to die, though few soldiers he still commanded did nothing to save him from his brother, Euron, who threw him off a bridge.
Tommen Baratheon
Tommen was kinder than his brother Joffrey, and softer too. The young king was naive to the ways of Westerosi politics. When the High Sparrow strikes, Tommen is helpless to protect Margaery and Cersei from the Faith Militant's wrath.
King Tommen may have ruled from the Iron Throne, but the gullible Lannister was ill-equipped to use any of the power under his control. He took his own life at the fall of the Sept of Baelor.
Renly Baratheon
Robert's death causes a squabble for the crown between his brothers. Although his status as the youngest brother puts him behind Stannis, Renly rejects inheritance laws and amasses an army to capture the Iron Throne.
Renly's alliance with the Reach awarded him a powerful army. Ultimately, however, this young and confident king was defeated by the mysterious shadow magic of Melisandre.
Euron Greyjoy
The second King of the Iron Islands featured in the series, Euron Greyjoy, proved to be a valuable ally for Queen Cersei during Season 7. Euron's Iron Fleet is an asset throughout Cersei's war against Daenerys and deals the Dragon Queen multiple crushing defeats.
Euron ruled the seas, but his strength waned on land and air. The Iron Islands were minuscule compared to the rest of Westeros, with fewer soldiers to defend them. It also didn't help that Euron was more interested in the thrill of the fight than actually ruling, even if he did plan to marry Queen Cersei to strengthen his domain's influence.
Sansa Stark
The series finale concludes with Sansa getting her Season 1 wish, as she becomes a queen. Sansa barters with her brother, King Bran, for Northern independence. Bran agrees and, with Jon exiled to the Wall, Sansa is crowned Queen in the North at Winterfell.
Sansa's power as the North's Queen is questionable, however. The Northern forces were battered by war, winter, and the White Walkers, leaving Queen Sansa more vulnerable than her fellow monarchs despite her being a legitimate heir to the Northern throne.
Robb Stark
Season 1 of Game Of Thrones sees Robb Stark inherit an immense measure of power. The Young Wolf is crowned King in the North by his people. The first Northern king in over three centuries commands the unified forces of his bannermen during the Starks' war with House Lannister.
Despite his many victories in battle, however, Robb's strength waned as the story progressed. Marrying Talisa and executing Rickard causes the Freys and the Karstarks to abandon him, considerably crippling his hold. Things would come to a tragic end for him and most of the Stark bannermen at the Red Wedding, where the Freys and Boltons sold them out to the Lannisters.
Stannis Baratheon
Stannis regarded himself as Robert's true heir and the rightful King of the Seven Kingdoms. Initially, the Baratheon monarch controlled less power than his younger brother. When Melisandre kills Renly with shadow magic, many of his forces flock to Stannis' side.
Stannis' forces take a heavy blow throughout the series. Many deserted him when his chances of victory begin to slim, before he finally perished in Season 5's failed attack on Winterfell (which, at the time, was under Bolton rule).
Jon Snow
Jon Snow became King in the North during Season 6's "The Winds of Winter." As well as being the second Stark in the series to claim the title, Jon was also the heir to House Targaryen as the trueborn son of Rhaegar and Lyanna.
Jon's forces were less in number than Dany's, depleted by the war with the Lannisters and the Battle of the Bastards. The Northern army was battle-weary, though Sansa's connection to the Knights of the Vale and Jon's union with the wildlings strengthened his power.
Joffrey Baratheon
The sheer power Joffrey inherited after King Robert's death amplified the young king's already vicious tendencies. As King of Westeros, few people could tell Joffrey no and live to tell the tale. Those like Sansa were forced to acquiesce his violent temper and impulsive tendencies.
Joffrey lost dominion of the North when he executed Ned. Despite this, the Lannisters manage to come out on top by establishing crucial alliances with House Bolton and House Tyrell.
Cersei Lannister
Most of Westeros despised her, but Queen Cersei still held a fair amount of power even before her short reign on the Iron Throne. When she takes the throne, Cersei allies with Euron Greyjoy in Season 7, combining the Ironborn forces with the Lannister army. In Season 8, the Lion Queen enlists the Golden Company in her war against Daenerys, though they weren't able to do much against a dragon.
Several regions of the Seven Kingdoms were at war with Cersei, hindering her power despite her dominion of the capital. The North remained under Jon Snow's rule, whereas Dorne and Highgarden had sworn allegiance to the Dragon Queen.
Mance Raydar
The King-Beyond-The-Wall was an impressive figure introduced in Season 3. Mance had no royal heritage or claim to the Iron Throne. Instead, the King of the Free Folk was chosen by his people to lead the wildings through the Wall, away from the dangerous White Walkers.
Mance Raydar surrenders to Stannis in Season 5 to spare his people, despite heading an impressive retinue of wildings, mammoths, and giants.
Robert Baratheon
The first king viewers meet, Robert Baratheon, possessed a considerable amount of power. Robert had little interest in ruling or monarchy. The governance of Westeros fell to the Hand and the Small Council whilst the drunk king's strength slowly faded.
Nevertheless, King Robert ruled over the entirety of Westeros, with each of the Seven Kingdoms swearing allegiance to him. His prowess in combat may have waned, but the Baratheon king remained one of the show's strongest characters.
Daenerys Targaryen
Daenerys Targaryen commanded more power than any other monarch in the series. The Targaryen queen's three dragons are formidable weapons invaluable in battle. Additionally, she had a legion of Unsullied soldiers and a khalasar of Dothraki screamers at her back.
Dany's death at the hands of Jon Snow suggests that love was her only weakness. With Drogon alone, she destroyed the Iron Fleet and King's Landing's defenses before laying waste to the city.
Bran Stark
The series finale concluded with an unlikely candidate as the new king: Bran Stark, the lost son of House Stark and the all-knowing Three-Eyed Raven. As the Three-Eyed Raven, Bran's powers are unparalleled. He can see visions of the past (and, seemingly, the future) as well as warg into the minds of humans and animals.
The reigning King of Westeros' omniscience gives him firm control over the country he rules. Daenerys was powerful, but her biggest weapons were vulnerable to Bran's warging abilities. Game Of Thrones featured a litany of powerful monarchs but in the end, the physically weakest but politically and magically most powerful of them all outlasted the rest of his contenders.