If you are looking for the most comprehensive lexical resource, you must look to the work of the White Fathers (Missionaries of Africa). In the mid-20th century, they compiled the definitive dictionary that is still used as the foundation for modern studies.
: Hosts versions of the English-Mambwe dictionary and grammar guide. Google Books mambwe dictionary pdf exclusive
: Beyond simple word definitions, it provides rules for Bantu noun classes (18 classes identified in Mambwe) and verbal structures. If you are looking for the most comprehensive