That isn't what happened during the Robert's Rebellion, when many lords were torn between vows to their King, and vows to their Lord. We don't see the massacre of prisoners as being acceptable really anywhere in Westerosi wars. If you're right, and that's just the way things are in Westeros...why was Tyrion arguing so forcefully against it? Why did Varys castigate Tyrion for not being able to restrain her, and Tyrion looking embarassed that he couldn't. Why does even Jon looked shocked when she did that? And not just killing them, but burning them alive.
Those weren't slavers. They were basically ordinarily Westerosi lords who happened to be on the losing side of a battle, and were actually defending their homeland against an army consisting of foreign troops. Burning them alive because they wouldn't kneel to you while their Queen was still on her throne was...messed up.
She has said, repeatedly, that she is the only rightful Queen, will insist on every other lord swearing fealty to her. And she has clearly demonstrated that she's willing to kill as many Westerosi soldiers as necessary to achieve that.
How is that not being power hungry?
My man, when you have allies and someone goes and wipes out your allies not once, but TWICE (remember Euron wiped out the Grejoy/Dornish fleet), are you telling me she's power hungry for "killing westorosi soldiers" AFTER THEY KILLED HER FORCES FIRST? You can't honestly believe that.
I'll give you an example of someone executing a prisoner of war, prior to a trial, in a far harsher manner than dragonfire.
Sansa Stark feeding Ramsay to his dogs.
Ramsay had no trial. Ramsay was a wartime captive.
Just answer this question: If the Throne was her primary objective, if that's all she cared about, why the fuck is she in the North. Why did she go save Jon Snow and his band of merry idiots? She didn't have to fly there. And lose a dragon. Does she get ANY credit for that?
And mind you, she swore to go North and defeat the Army BEFORE Jon swore fealty.
Back to the Tarly's. That was not their queen until about 8 minutes prior when Randyll decided to betray House Tyrell. Their queen was Margaery Tyrell who was murdered, totally and completely unjustly, by Cersei Lannister. ALong with almost the entire rest of House Tyrell.
And Randyll said "Nah, you know what, fuck House Tyrell I'm joining the Lannisters."
That's.....treason. Like no matter how you slice it up. The Lannisters openly made war with House Tyrell and Randyll Tarly turned his back on them.
Yes, she wants the Throne. So did Stannis and Renly and Littlefinger and a whole host of other people.
She freed slaves across the sea. Stayed in Mereen. to try and keep said slaves from being re-enslaved.
She shouldn't have burned Dickon. But fuck Randyll Tarly. He threatened to murder his own son and sentenced him to a life at the wall. He can go get bent.
EDIT: More examples: How about the Mountain raping and killing Elia and her children and Robert PARDONING him for it? Now the Mountain is clearly evil...but what does that make Robert? A totally innocent wife and two tiny, small children. Doesn't even compare to soldiers captured in battle, does it? Yet Robert, essentially, gave the ok to the practice.
DOUBLE EDIT: BTW Jon did not execute Janos Slynt because of all of that other shit he did. He executed him because he wouldn't go to Greywatch Tower (I think). ANd he had that "I'm a badass" face while doing it.
So differentiate it for me. Because the Tarlys were also given a choice to go to the Wall. People keep forgetting that. It was proposed and they refused.