Hints That Dany Was Always Mad (spoilers)
Or always a cruel sociopath narcissist like her brother.
At first, it wasn't obvious because she was being victimized by her brother. Then Drogo when they first married and Drogo's people when she was widowed. We felt sorry for her and cheered for her success.
But, as she gained power, it came out more. An example of her narcissism is how she needs to be presented:
"Queen Daenerys Stormborn of the House Targaryen, the First of Her Name, Queen of the Andals, the Rhoynar and the First Men, Lady of the Seven Kingdoms and Protector of the Realm, Lady of Dragonstone, Queen of Meereen, Khaleesi of the Great Grass Sea, the Unburnt, Breaker of Chains and Mother of Dragons."
Even King Robert didn't have a zillion titles.
She constantly congratulates herself when she helps people and adds another title. Even the witch, Mirri Maz Duur had a good point. She was supposed to be grateful to Dany even though her village was destroyed and its people killed and she had been raped for weeks. It's ALL about Dany.
Dany has a huge ego and wants to be worshiped. If not, she incinerates. In her twisted mind, it was always necessary.
Not once, does she show any compassion or empathy unless it's to be worshiped or gain followers aka: putting on an act. Her brother was scum, but he died in a gruesome way and she didn't even flinch. Jon flinched when Varys died.
The other leaders kill too, but it's rare and difficult for them and the reason is usually because of a crime committed. Dany is killing to get people to follow her which is what all tyrants do.
How many times has she threatened Tyrian and Jon? It's only a matter of time before she will kill them.