Well yeah, Lantsov was a pig, but the Darkling could have just killed the monarch and his line if that was the only reason. Or care to find out who the other brother was and put him on the throne. But the Darkling doesn’t forgive does he or share his power now that he has it. He’d rather slay all the Grisha to get to Alina. Because that is what he wanted power through Alina. And what did Genya get for her years of loyalty or Sergei who betrayed where the spinning wheel was, got ripped to shreds as a thanks. The Darkling wasn’t a righteous revolutionary he was just going to be another kind of tyrant.
This is from that reddit comment about why everyone sided with the darkling.
Well yeah, Lantsov was a pig,
When you start a rant like this, and continue to something completely else, you're already dismissing the above.
Why bother with systematic issues, when you can find a single scapegoat, right?!
but the Darkling could have just killed the monarch and his line if that was the only reason.
I mean... that's what he tried to do, when he got tired of being nice, since it lead to nothing?
He allowed Genya to poison the King. HE was the one to kill Vasily (since his nice brother didn't have the guts to do so). He had his babies eat all the Lantsovs gathered to celebrate Nikolai's birthday. He incapacitated the secondborn bastard.
By the end of Ruin and Rising he had a clear path to the throne. Nobody to seriously challenge him. (Unlike the incompetent Golden Prince in later duology.) ¯\_(ツ)_/¯
Or care to find out who the other brother was and put him on the throne.
Why? If you'd read any of his dialogues, you'd know he did that over and over, only to see anything he achieved crumbling as soon as "the nice" monarch dies.
“The people would love you for a time. But what would they think when their good king aged and died, while his witch of a wife remained young? When all those who remember your sacrifices are dust in the ground, how long do you think it will take for their children or their grandchildren to turn on you?”
Ruin and Rising- Chapter 9
What had changed? The answer was everything. Kings lived and died. Their sons were honest or corrupt. Wars ended and began again—and again and again. Grisha were not accepted; they were resented in Ravka and hunted abroad.
Rule of Wolves- Chapter 33
But the Darkling doesn’t forgive does he or share his power now that he has it.
No, he doesn't forgive, because his experience says they'll stab you in the back AGAIN.
As for him sharing his power... How do you know? Do you have access to some previously unpublished pieces?! We never got to see Second Army structure- and army HAS TO have it by definition-, and the only glimpse of his rule includes listening to "supplicants", accompanied by “I will take it under advisement.”, which is hardly an action of someone disinterested in others' opinions.
Ruin and Rising- Chapter 3
He literally offers Alina a throne in the same chapter, when we're at it:
“There are two thrones on that dais. You could see me anytime you liked.” ... “I sought Morozova’s amplifiers for you, Alina, that we might rule as equals.”
He’d rather slay all the Grisha to get to Alina.
Which Grisha? Alina's "maybe fifty" traitors from "hundreds stationed throughout Ravka"? Because the later were either murdered by First Army, in hiding or "had sought out the Darkling".
Siege and Storm- Chapter 15, Shadow and Bone- Chapter 10 and Siege and Storm- Chapter 12, respectively
Because that is what he wanted power through Alina.
Well, then he'd picked the perfect person for it, wouldn't he?
The one, who just wants to crawl back under the rock...
And what did Genya get for her years of loyalty
I could ask what he got for years of close co-operation on the most dangerous kind of plans, and a blessing to off her otherwise untouchable abuser. Especially since the guy, who send the abuser to comfy "exile" with no restrictions regarding access to more victims to rape, "earned [Genya's] loyalty forever".
King of Scars- Chapter 23
She let a crucial asset go, when ordered the direct opposite. A bit of scarring is simply era-appropriate, although usually it would be delivered by a thick whip with much less precision. And a smaller chance to survive.
or Sergei who betrayed where the spinning wheel was, got ripped to shreds as a thanks.
Sergei was twice a traitor. First he chose not to heed the Darkling's call and join the side that planned to slaughter him (, his and a whole shitload of bystanders). Second he betrayed the side he thus picked.
While I understand why he did the later- Alina treated him like a burden, and he had very little support after a horrifying trauma- he's still less than reliable, and the Darkling's action was that of a general in middle of a conflict. Sure, quartering is "officially" a bit less modern than 19th century, but it's not such a stretch.
The Darkling wasn’t a righteous revolutionary he was just going to be another kind of tyrant.
Because tyrants usually have trust of their closest advisors, sit on the ground and share meals with their subordinates.
“Did you know I had two brothers?” Ivan asked abruptly. The familiar smirk was gone from his handsome face. “Of course not. They weren’t born Grisha. They were soldiers, and they both died fighting the King’s wars. So did my father. So did my uncle.” “I’m sorry.” “Yes, everyone is sorry. The King is sorry. The Queen is sorry. I’m sorry. But only the Darkling will do something about it.”
Shadow and Bone- Chapter 20
In the light from the fire, I watched the oprichniki sitting side by side with the Grisha. Some of them had already drifted away from the fire to bed down for the night. Others had been posted to the first watch. The rest sat talking as the flames ebbed, passing a flask back and forth. The Darkling sat with them. I’d noticed that he had taken no more than his share of the grouse. And now he sat beside his soldiers on the cold ground, a man second in power only to the King.
Shadow and Bone- Chapter 5
Once again you can see reddit side of the fandom has nothing of value to offer. No fresh view, a waste of time.