"Bad Catholic" as opposed to perfect "Sinless Catholic"?
All Catholics are bad when they sin.
There are those who call themselves Catholics, go to Mass on Sundays, give alms, etc. But they do not work on aligning their thoughts and beliefs with the Magisterium. In fact, they see no reason to do so, see no duty to engage with the Magisterium.
They profess Catholic Xtianity with their lips, they think of themselves as Catholic, but they don't take the Gospel into their lives and minds. They've dipped their toe in, but they haven't taken the personal or intentional plunge.