Yoda is one of oldest Jedi masters and was once on the Jedi council. He is believed to be the strongest force user due to his age and experience with using the force. Dieing at the age of 900 he was the oldest Jedi to ever live in the movies and trained several generations of Jedi. Not much is actually known about this old Jedi master for example his birth palce, race and his master. However throughout his lifetime he has been in many battle show casing his skills. Some of these many battle can be read about in the link below
Yoda may be the strongest Jedi in the current cannon universe however there are other Jedi who might measure up or might currently measure up as Jedi battles did not take place during the movie only Sith vs Jedi and this site debates abilities experience and force capability to figure out my own personal opinion’s best force user.