The fact that Fogg was willing to risk both his life and his fortune to rescue Aouda (from the Raja's men) and Passepartout (from the Sioux).
The penultimate chapter, when Fogg believes he has lost his wager and is ruined. Aouda, for whom Fogg sacrificed travel time to rescue from certain death and then invited her along on his trip home, feels profoundly guilty that she may have cost him his bet, which Fogg thoroughly denies. Regardless, Aouda, already in love with Fogg, offers to marry him in part to help him live through his difficult future. At this, Fogg's Stiff Upper Lip caves in at last and accepts declaring his love for this gracious lady. Even better, when Passpartout goes to make arrangements for the wedding, he discovers that there is actually still time to arrive at the Reform Club to win the bet and that Fogg is able to arrive Just in Time to do so.