What are differences between Kurtz and Marlow in Conrad's Heart of Darkness?

There are a great deal of differences between Kurtz and Marlow in Joseph Conrad's Heart of Darkness, most of which stem from the fact that Marlow functions primarily as a narrator, while Kurtz often serves as the true focus of Marlow's narrative. As such, we learn much about the development of Kurtz as a character, while we learn much less about Marlow.

Though Marlow is not without his own complexities, his primary duty in...

There are a great deal of differences between Kurtz and Marlow in Joseph Conrad's Heart of Darkness, most of which stem from the fact that Marlow functions primarily as a narrator, while Kurtz often serves as the true focus of Marlow's narrative. As such, we learn much about the development of Kurtz as a character, while we learn much less about Marlow.

Though Marlow is not without his own complexities, his primary duty in the story is to relate the tale to the sailors waiting on the Nellie. While Marlow has intriguing personality quirks of his own (he quickly reveals himself to be an intellectual but cynical individual), the reader is given little insight into Marlow's deeper being, as he exists in the story mainly to observe and comment on the actions of others. 

Kurtz, on the other hand, is the definition of charisma. Originally a principled and idealistic individual, Kurtz quickly becomes drunk with power, and his grim descent into madness is one of the main points of the novella. As such, while Marlow tends to avoid the spotlight, Kurtz is notable for commanding attention with his hypnotic voice and infectious ideas. As such, the primary difference between Kurtz and Marlow is that, while Marlow is relatively nondescript and undeveloped (in general terms), Kurtz is a vividly drawn character with immense depth who largely commands the main arc of the narrative.