What was Jack Lemmon's final movie performance?

An uncredited role in "The Legend of Bagger Vance" was his last film.

https://en.wikipedia.org/wiki/Jack_Lemmon

There are rumors that Walter and Jack Lemmon were in talks to do one final film together (as they knew they were both fading fast from cancer). Talks were to begin in late 2000, but Walter became critically ill very shortly after shooting on Hanging Up wrapped, and he never recovered.

http://www.findadeath.com/Deceased/m/Matthau%20Lemmon/www.htm

The Odd Couple II is the 1998 sequel to 1968's The Odd Couple. It reunites Walter Matthau and Jack Lemmon in their last film together, and it was Jack Lemmon's final credited film before his death in 2001.

https://en.wikipedia.org/wiki/The_Odd_Couple_II