Daenerys Targaryen, played by Emilia Clarke, is one of the most intriguing characters in the long list that Game Of Thrones has. The biggest reason why stems from her character arc.
Daenerys, begins as an innocent, lost young woman and grows into a power-hungry dictator. She has many chances to make the right decision. Unfortunately, she does not due to her addiction to being superior.
Killing Viserys
In Season 1, Episode 6, Daenerys makes her first malicious decision. Daenerys watches and allows her brother, Viserys, to die. Yes, her brother was a terrible person, but that is utterly irrelevant. By Daenerys allowing her brother to be killed, watching while his head melts, she gets her first taste of death. This makes the order of each kill after much easier.
Daenerys knew her brother was in the way of her success, so she let him burn. After watching him burn, she adds, "He was no dragon, fire cannot kill a dragon."
Killing Drogo
Most likely, Drogo was going to die from his wounds, and the spell cast upon him. However, that does not necessarily justify what Daenerys did. In Episode 10 of Season 1, as Drogo lay on his bed to rest, Daenerys smothers him with a pillow. By doing so, she has experienced what it is like to kill a man, let alone the fact that it is her husband.
Burning Mirri Maz Duur Alive
In Season 1, after Drogo passes, Daenerys confronts Mirri. Mirri is asked to heal Drogo from his wounds with her witch-like abilities.
Mirri resists from treating Drogo because of how she was mistreated, having been raped by three men, and seeing her city burn. Mirri refraining from helping Drogo, ultimately caused her demise as Daenerys burned her alive.
Receiving Her Dragons
Daenerys is gifted three dragon eggs as a wedding gift in Episode 1, Season 1. Later in the season, her dragons hatch, and she has to choose what to do with them. Being the Mother of Dragons is accepting to have the most powerful weapons in all of the lands. Once given that power, it is up to her to make right decisions with that. Unfortunately, she does not feel that way, as she uses her dragons as a way of advantage throughout the entire series.
Crucifying Meereen Masters
Undoubtedly the Meereen masters were terrible people; however, ordering 163 men to death without knowing who is innocent or guilty is too much. Daenerys' main concern is sending a message to all that she has no compassion for you if you aren't one of her men. Crucifying the Meereen masters is a prime example because she murders them in such a cruel way. Barristan Selmy tries to suggest that it is better to answer injustice with mercy. To which Daenerys replies, "I will answer injustice with justice." This is even more evident in season six when Daenerys states what she will "return the Meereen cities to dirt."
Ordering Her Dragons To Kill
In the episode, Valar Morghulis, Daenerys orders her dragons to kill for the first time. It is to defend herself against Pyat Pree, however, she does order them to kill him.
Now that Daenerys knows she can order them to kill whomever she wants, she realizes just how dangerous she can be.
Kicking Jorah Out
From the moment Jorah Mormont first laid eyes on Daenerys, he has been in love with her. Jorah would do nearly anything to protect her, and for the majority of the series, he is her right-hand man. This is why when she kicked Jorah out of her city in Season 5, Episode 8, fans were beyond infuriated. Daenerys pushing away those who care about her most is the exact reason why she was so successful at being so maniacal.
Jorah does return later on in the series; nevertheless, Daenerys turned her back on him with little hesitation.
Burning Randyll Tarly
Tyrion and Sam are right up there next to Varys as some of the most genuine characters in the series. Unfortunately for both of them in this instance, they have sided with a Mad Queen. After winning the battle against the Lannister Army in Episode 4 of Season 7, Daenerys gathers up what enemies remain and gives them a sinister and dictatorial choice of joining them or dying. Randyll Tarly, and his son (Sam's brother) do not join her. Because of this, they are burn to ash.
Killing Varys
Varys had one of the kindest hearts in all of Game Of Thrones. An innocent man that would not have hurt a fly. All he wanted was to have the right king in place. With that said, Daenerys being her typical self decided he was a threat and had him killed. This was the breaking point for so many fans, as Varys wanted the same as the viewers watching from home.
Destroying King's Landing
In season 8, Daenerys commands her army to attack King's Landing due to her distaste for Cersei. She feels that if she can take over King's Landing, she will be the ruler of all kingdoms. At this moment, she has completely transformed into the Mad Queen. She is so blinded by power that not even Jon, the one she "loves" can keep her from burning the city to ashes. She rides her remaining dragon to King's Landing and kills every innocent person in the city.