Doflamingo believed his strength was sufficient. Even if he could not win, at least he would not die. Naturally, there was no reason for him to fear Kaido.
Besides, Kaido was currently busy suppressing Wano Country and might not be willing to provoke a formidable enemy like Doflamingo.
Although Kaido had appeared as a reckless brute when he first showed up in the manga, his treacherous and cunning nature had soon been exposed. Doflamingo had merely killed an ordinary Zoan Fruit user under his command, not one of his All-Stars.
He was only an ordinary Zoan Fruit user. Kaido probably would not even learn about what happened here. Even if he did, Kaido would not take it to heart.
Doflamingo could believe that Kaido might come looking for trouble after learning of it, but saying Kaido would fight him to the death over this was overthinking it.
After all, Doflamingo was not some Supernova without backing. As the strongest rising talent of the new generation in the Marines, a Marine officer being groomed as an Admiral, if Kaido truly beat him to death, then no matter how much the World Government wanted to maintain the balance, the Marines would have to mobilize their entire force to eliminate Kaido.
As for Kaido's claim that he could not be killed... heh, it was best treated as a joke.
Up to this point in the manga, Kaido had not displayed any trait that made him impossible to kill. At most, his Armament Haki and physical toughness gave him higher defense and thicker vitality.
Ordinary torture devices, guillotines, iron chains, and the like could do nothing to him. But if you had a powerhouse like Garp hammer his head for ten minutes, see whether he could smash Kaido's brains out!
To put it bluntly,