“Littlefinger was born with no lands, no wealth, no armies. He has acquired the first two, how long before he has the army? Perhaps you’ll laugh but I know him better than most and this is the truth: Littlefinger is one of the most dangerous men in Westoros.” – Varys
A lot of people talk about how Littlefinger was the one to initiate the story because he’s responsible for Jon Arryn’s death. In the pilot of the show, Catelyn goes to meet Ned in the weirwood to tell him of Jon Arryn’s passing and to inform him that the king was making his way to Winterfell. Robert Baratheon arrived and asked Ned to be Hand of the King. A letter then came from Lysa Arryn, which said that the Lannisters killed her husband. This is the reason that Ned decided to go with Robert to King’s Landing because Ned felt that his friend needed his protection and so the war between the Lannisters and the Starks began. We learn later that the Lannisters did not, in fact, kill Jon Arryn but it was his wife, Lysa, who did so because Littlefinger asked her to. To make sure that the Starks took this bait, Littlefinger lied that Tyrion sent the dagger sent that attempted to kill Bran.
While Robert Baratheon lay dying, Ned called on Littlefinger to confide in him about his plans to hand the Seven Kingdoms over to Stannis. Ned was never one to play the game of thrones and when Littlefinger realized this, he deceived Ned into thinking that he too was interested in honoring the entitlement of Robert’s rightful heir. Instead, he sold the City Watch to Cersei and used them to butcher Ned’s men, seize Ned himself and capture Sansa.
Ned died and after some time Theon conquered Winterfell and claimed to kill Bran and Rickon. Littlefinger went to see Catelyn and tried to convince her to release Jaime in exchange for her daughters. Poor Cat was in a vulnerable position so when it looked like her son’s soldiers were going to kill Jaime, she released him on the condition that he would return her daughters to her. This was the beginning to Robb Stark’s end because Robb, of course, didn’t understand why his mother did what she did and was furious with her. He alienated her and went right into Talisa’s arms, losing the Freys and carving his death in the process. Robb also lost the Karstarks when Lord Karstark killed 2 innocent Lannister boys due to his resentment at the loss of his opportunity to avenge his sons.
Littlefinger was the one who introduced an alliance between the Tyrells and the Lannisters. This alliance helped the Lannisters win the battle on Blackwater which Stannis would have won otherwise. The alliance also meant that Joffrey married Margaery instead of Sansa. Littlefinger was the one who let Cersei know about Lady Olenna’s plot to marry Sansa off to Loras and so Tywin arranged a marriage between Sansa and Tyrion.
In season 4, Littlefinger conspired with Lady Olenna to kill Joffrey thereby “saving” Sansa in a way that made her look guilty af. Tyrion and his wife were blamed for the murder and Tyrion alone was sentenced to death in Sansa’s absence. Joffrey’s death led to Oberyn’s death which led to Tywin’s death which happened during Tyrion’s escape. Without Tywin or Tyrion, the Lannister family is doomed and that is precisely why Littlefinger switched camps. He ended the Starks, now he’s doing the same with the Lannisters. Behind Cersei’s back, he arranged a marriage between Ramsay and Sansa to secure the Boltons’ hold on the north.
Littlefinger is the person everyone in Westoros should be watching out for. Strangely, only Varys has been able to foresee the damage he can cause and how adept he is at using everyone as pawns. Where is he anyway? We haven’t seen him in a couple of episodes which means he must be hatching something dastardly. And how does he travel? Because he gets everywhere he needs to be so quickly.