This is dependent on a world where immortality is expensive because it's difficult to actually make someone immortal rather than because it's difficult to figure out how to make someone immortal. For all we know, immortality is as simple as a one-time injection into an egg cell, and the challenge is almost entirely in figuring out what to inject.

Also, how much is the death of bad individuals actually contributing to making the world a better place? It seems to me like the various abuses of robber-barons and tyrants past and present are perpetuated by institutions built around them rather than their own personal capacity to affect the world. A king in exile on a remote island or a Rockefeller driven to bankruptcy can remain unchanged as a person while losing virtually all of their capacity to impose their will on the world, while a kingdom or corporation can keep going centuries after the death of its leader if conditions stay favorable.