Both Uses of

prepossessing
in
The Count of Monte Cristo

Attracted by his prepossessing appearance, he renewed his offers of an engagement to Dantes; but Dantes, who had his own projects, would not agree for a longer time than three months.†
Chpt 22-23 *

while the flatness of his forehead, and the enlargement of the back of his skull, which rose much higher than his large and coarsely shaped ears, combined to form a physiognomy anything but prepossessing, save in the eyes of such as considered that the owner of so splendid an equipage must needs be all that was admirable and enviable, more especially when they gazed on the enormous diamond that glittered in his shirt, and the red ribbon that depended from his button-hole.†
Chpt 45-46

Definitions:

(1) (prepossessing)
creating a favorable impression ahead of time
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Do note confuse this with prepossess or prepossesses or prepossessed which mean to be preoccupied or to influence opinion ahead of time.