Which is the best quality of an engineer?

Team Management, Stress Management, Ethics 

PROFESSIONALISM AND CREATIVITY

Creative thinking is the best quality of an Engineer. And smart working also a quality of an Engineer

ATTITUDE, SKILL and KNOWLEDGE

The best quality is first to NOT be an engineer: LISTEN! and then be the engineer to solve the problem, That's the biggest problem with engineers.

Material quality is important

They love numbers which others hate

Problem Solving is the best qualify of an engineer. 

1. Possesses a Strong Analytical Aptitude
2. Shows an Attention to Detail
3. Has Excellent Communication Skills
4. Takes Part in Continuing Education
5. Is Creative
6. Shows an Ability to Think Logically
7. Is Mathematically Inclined
8. Has Good Problem Solving Skills
9. Is a Team Player
10. Has Excellent Technical Knowledge

Best Engineer means professionalism and consistency in the work to achieve desired or required goal.

Technologically superior from others, an Engineer can almost do anything related to household and (somewhat) industry while others like accountants and bankers etc, will probably hire someone to do it for them.