I feel that a great biography not only has to be about an interesting character, but needs to be delightful to read.

What’s the best biography you’ve read by these standards?

Richard Feynman comes to mind. Entertaining.

Da Vinci - Isaacson 

And jic of interest.

farcaster://casts/0x297297d473b8805d406efdfe0ccd53beb5e27fb41db5ea51aefdb4dff3f6a537/0x297297d473b8805d406efdfe0ccd53beb5e27fb41db5ea51aefdb4dff3f6a537

Atoms in The Family — great biography of Enrico Fermi (one of the most versatile physicists of the 20th century) written by his wife. Captures the “feel” of an important era in history and in the development of modern physics. 

https://a.co/d/6NAqGTn

The first that comes to mind is The Man Who Loved Only Numbers about  Paul Erdos.