the best part of (something)
1. The majority of something. I'm sorry I'm late—my doctor's appointment took the best part of an hour.
2. The most enjoyable or exemplary aspect of something. No, the cream filling is definitely the best part of this dessert! The introduction was the best part of your term paper. After that, it meandered for a while.
best part of something
almost all of something; a large part of something; the major part of something. The discussion took the best part of an hour. The best part of the meeting was taken up by budgetary matters.
the better/best part of something
most of something: I worked at the camp for the better part of the summer.He had lived there for the best part of fifty years.