Chasing my tail

I have been asking a co-worker to fix something they broke for over 2 months now. It was critical in July and is critical again this month. I am about ready to strangle. It always amazes me how some people can breeze through their jobs, not taking responsibility, taking advantage of their co-workers. This person even laughs about how easy they believe they have it with this job, while we grit our teeth because others are left picking up the slack, cover or wait for them.