Many people classify sins into “major” and “minor”.  It doesn’t mean the major are bigger and the minor are smaller, we cannot overlook minor sins. They just aren’t listed as having a specific punishment. 

The measure of our sins is not in whether they are major or minor, but in whether or not they hurt other people. 

Sh. Yahya Ibrahim defines major and minor sins and clarifies which sins are among the most harmful to commit.