Yinsen was still agonizing over the color of his Susanoo when Danzo, over on the other side, had already been driven to question his entire life.
But no matter what state he was in, it did not stop Itachi Uchiha and Sasuke from joining forces to gang up on him.
Tsunade had originally hesitated over whether she should spare Danzo's life, but once Danzo used Wood Release and proved that Yinsen's earlier words had not been nonsense, she no longer had any intention of letting the old bastard live.
The Sharingan, the First Hokage's cells, and Danzo had all been among the culprits behind Kakashi's father's death. Unknowingly, the place had filled with an atmosphere of 'Danzo must die.'
In the end, he was indeed beaten to death without any suspense!
Izanagi was an extremely powerful Forbidden Jutsu. It could turn any unfavorable situation into an illusion, and there was naturally a reason it was called forbidden: after using Izanagi, the Sharingan would permanently lose its light—in simpler terms, it would be ruined.
Danzo had installed a whole pile of Sharingan in his arm, but Sharingan placed a tremendous burden on their user, especially a user who was not from the Uchiha Clan. Even with the First Hokage's cells strengthening his body, Danzo could not endlessly pack every inch of his arm with Sharingan.
His limit was ten Sharingan, plus the Mangekyo he normally kept in his eye socket. Any more would not help him; they would instead become a burden.
So even if Danzo sacrificed all ten Sharingan to cast Izanagi, he would only gain ten more lives.
If it had been Sasuke, he might have needed to feel things out first before figuring out the proper way to deal with it, just like when Sasuke fought Danzo in