Which are the most important key skill should be known by a electronics engineer to enhance his career?

well to honest you should be best in basic in very field, and perfect on your last work what you did, when it comes to skills i think confidence, commitment, and leadership skills matter more then engineering skills and interpersonal skills. 

take some courses it is called   LET networks &physical layer modeling of LT Air interface . And Data associated and professional.also training on ARM embeded system development

Good luck

Communication skills and interpersonal skills. 

A good background about electronic. 

Be motivated