She murdered some Masters without a trial. She burned alive a group of Khals. Granted, neither of them could be considered "innocent" exactly, but neither did they outright provoke her. Even earlier, she was essentially happy when Drogo declared that he will slaughter people in Westeros. I mean, she smiled at this: "I will kill the men in iron suits, and tear down their stone houses. I will rape their women, take their children as slaves, and bring their broken gods back to Vaes Dothrak." Punishment of the wine seller was beyond justice, it was vengeance, it was torture. Fact that their targets in early seasons had been invariably guilty doesn't mean she did not have capacity, and even penchant, for cruelty. When she arrived at Quarth, she acts entitled (though maybe she truly was, not sure on rules of conduct in that area). Once refused, she threatened that "When my dragons are grown, we will take back what was stolen from me, and destroy those who had wronged me. We will lay waste to armies and burn cities to the ground. Turn us away, and we will burn you first." And then: "I will take what is mine. With fire and blood, I will take it." She also killed Doreah, handmaiden who had enabled her marriage to Drogo to be successful, Now, Doreah apparently did betray her, so death sentence was logical reaction; but the manner in which it was carried out - basically burying her alive - was unnecessarily cruel. And all of that was done without a trial. When Stannis believed Davos had betrayed him, he still allowed Davos to speak in his own defence; Daenerys rarely if ever allowed those she deemed guilty to defend themselves. After conquering Mereen, Daenerys crucified 163 masters. There was no trial, no established guilt; just random selection. Just like everything above, it was vengeance disguised as justice. And we later learn that some of those 163 were innocent. She did this despite Jorah Mormont's advice to the contrary. Later she said "They can live in my new world or they can die in their old one." So basically, "submit or die". Selmy later warned her that the Mad King "gave his enemies the justice he thought they deserved", and every time it made him feel "powerful and right". At this point, he could have been just as well describing Daenerys herself. She also apparently enjoys watching her enemies burn, such as when she feeds slave masters to her dragons. She threatened Hizdrahr with burning Meereen to the ground. Now, her burning of khals was a justified self-defence. But notice that she takes pleasure from the act: Notice at 4:00 that she is smiling. She enjoys watching her enemies burn. In episode 6x6, she speaks to her khalasar. "Will you kill my enemies in their iron suits and tear down their stone houses?"  This is clear sign that she has set herself on the "Fire and Blood" path. She is after conquest, and she is after vengeance. Later on, she threatened to crucify the maesters, and return their cities to dirt (that is, burn them all). And when Tyrion warned her of what she was doing, that she was becoming similar to the Mad King, she just dismissed his advice. She outright told Varys "If you every betray me, I will burn you alive". Varys did betray her, but only after she betrayed her own people. Daenerys burned Tarlys alive as an intimidation tactic. You can say that they deserved to die, and even burning them for intimidation may be considered acceptable approach to reduce casualties in long term, it was still cruel. Traditional and responsible way of execution would be by beheading. Dany also showed little emotion when she delivered news to Sam. Now, on its own, it doesn't mean much; some people simply don't express emotion much, or simply don't feel emotions very strongly. But later, when she was with Sansa, she was all smiles. This implies that she had been manipulating people - including viewers - all along. If idea that she had been falsifying emotions is true, it would make her into a high-functioning sociopath. She has also maintained respect for her father and brother. Her expression of jealousy towards Jon parallels how Viserys expressed jelaousy towards her in season 1. And lastly, she developed serious messianic complex: "I'm here to free the world from tyrants. That is my destiny. And I will serve it, no matter the cost,"     This goes into little more detail: https://www.businessinsider.com/game-of-thrones-daenerys-mad-queen-foreshadowing-2019-5