Tyrion is the only Lannister that paid all his debts in Game of Thrones. He was named Hand to Brandon Stark, a position he was forced to take by the new king as a punishment. Bran told Greyworm that Tyrion would spend the rest of his life correcting the mistakes he had committed in his life, but what were these mistakes?
Tyrion was born an outcast whose father almost dumped in the sea because he was an imp. He lived all his life fighting for his survival as he tried to prove himself as useful despite his appearance. While Tyrion's intentions were always the best, he didn't always make the best decisions, and some of his political tricks ended horribly wrong.
Best Of All: Advising Jon Snow To Kill Daenerys
After spending the better half of his time in Game of Thrones advising Daenerys hoping to save the common folk, Tyrion was forced to commit treason to finally accomplish his duty. It wasn't his fault that Danerys went mad. He had tried everything to ensure that she didn't become the queen of ashes, but when it happened, he had to do something.
"Sometimes, duty is the death of love," Tyrion told Jon Snow, reversing Maester Aemon's advice to save the realm. He had made the mistake of not listening to Varys and after the annihilation of King's Landing, having Jon kill Daenerys was the only way for him to correct the injustice.
Worst: Taking Myrcella To Dorne
Myrcella Baratheon's death was one of the saddest in the show, and it was all because Tyrion underestimated the Martells' hatred for Lannisters. Cersei was opposed to the decision of sending her daughter to the island, but Tyrion thought she would finally get Dorne to support the Lannisters.
His idea of having one less enemy for Joffrey was great, but there was no way the Martells could overlook Tywin's past crimes against Elia Martell and her children.
Best: His Trial By Combat In The Eyrie
Catelyn Stark was a smart woman that wanted justice for her family but killing Tyrion wasn't the way to get it. Lyssa and Catelyn didn't care much about Tyrion's guilt, though; they only sentenced him to death because he was a Lannister. The great Tyrion Lannister dying by being thrown through the Moon Door would have been the saddest death of the show.
Tyrion was lucky enough to win Bronn's trust before getting to the Eyrie. Bronn's skills with the sword were the only thing that could save him that day, and Lyssa and Catelyn being religious, wouldn't reject the 'verdict of the gods.'
Worst: Accepting To Be Hand To Joffrey
Tyrion didn't have much of a choice when his father sent him to King's Landing as Hand to Joffrey, but it was always going to end in disaster. Joffrey was a spoiled boy that didn't know what it meant to be king and who didn't deserve the service of a man as smart as Tyrion.
Being Hand to Joffrey exposed Tyrion's talent as a diplomat but also made him enemies with Cersei and other powerful people in King's Landing. It nearly got him killed, and it was the reason he ended up in Daenerys' service in the first place.
Best: The Battle Of Blackwater Bay
During his trial for the murder of Joffrey, Tyrion burst at the crowd for being ungrateful because he saved them all from Stannis Baratheon. He was actually right because his plans with the Alchemist's Guild and Bronn saved the city from bot Cersei's stupid plan and Stannis' army.
Cersei planned to have the City Watch fling pots of Wildfire at Stannis, and as Bronn said, that would have meant Stannis throwing some back at them, things breaking then boom, King's Landing on fire. Tyrion had the Alchemists produce Wildfire for him, then delivered it to Stannis perfectly on unmanned ships.
Worst: His Trial By Combat In King's Landing
The moment Tommen recused himself from Tyrion'strial naming Tywin as the judge of Tyrion's fate, Tyrion was a dead man. Tywin never liked his son and would have gladly seen him die, even for a crime he didn't commit. Tyrion's best option was to look for a way of escaping from that dungeon from the moment the trial started.
Choosing trial by combat only meant that whoever chose to fight for him would face The Mountain, something no one would agree to. The stakes were too high, even for Bronn. His decision led to Oberyn's death, which only worsened the relationship between Dorne and King's Landing.
Best: Killing Tywin
Tywin Lannister was a strong man that understood the politics of The Seven Kingdoms well, but he was heartless and deserved to go. He was forcing everyone to bend to his will, forcing Tyrion to marry Sansa, Cersei to marry Loras, and the Small Council to worship him. Under his rule, The Seven Kingdoms were quickly being shaped in his image with lots of heartlessness.
He was willing to break the rules and cross boundaries to achieve his mission, including murdering the Starks in cold blood at the Red Wedding and handing over the North to the Boltons. Tyrion saved Westeros when he killed Tywin because no one else was going to stop him.
Worst: The Dragonpit Summit
Tyrion was brave when he decided to go into The Red Keep for a face to face meeting with Cersei. Cersei, just like Tywin, never liked Tyrion and would have killed him. Tyrion's tongue saved him, although his wit seems to have failed. He was one of the smartest people in the show, but he didn't see Cersei lying to him in the face.
Cersei never meant to send an army North to fight the dead, and Tyrion could have seen that when she said she wasn't afraid of the Wight she had just seen. Tyrion was stupid enough to go North on the promise of the most cunning woman in The Seven Kingdoms.
Best: Advising Dany To Work With Jon
Jon Snow and Daenerys made one of the best couples in Game of Thrones, creating the powerful force that finally defeated the Night King but would never have happened without Tyrion. He advised Daenerys to allow Jon to mine the Dragonglass in Dragonstone while also encouraging Jon to give Daenerys a chance.
Tyrion understood the need for Daenerys to ally with The North. Unlike the rest of the southerners, Tyrion didn't dismiss Jon's claim of White Walkers beyond the wall. His advice created the alliance that saved The Seven Kingdoms in The Battle of Winterfell.
Worst Of All: Betraying Varys
Varys had been loyal to House Targaryen since the days of The Mad King, but he realized that Daenerys was the wrong Targaryen to sit on the throne. His faith in the Mother of Dragons ended when he watched her burn Randall and Dickon Tarly despite the pleas of everyone present.
She was going to make The Mad Queen, and Varys knew it; all Tyrion had to do was give him the chance to correct his mistake. Tyrion instead chose blind loyalty over duty, something he had never done throughout the show. Varys' death remains the biggest of Tyrion's mistakes.