Paul McCartney and John Lennon had one of the best songwriting partnerships in one of the biggest bands in the world, The Beatles. However, they knew how to get under each other’s skin. In their partnership, they’d often write songs separately. Paul would write sweet songs while John would sometimes write sadder angstier tunes. They were sweet and sour, yin and yang, but they always finished every song off together. Despite those beautifully creative moments in their friendship, Paul and John could be brutal to one another.
Source: cheatsheet.com