Catholics who do not try to follow the faith. An example is Catholics who use contraception, and insist that they are right in doing so and do not need to confess.
Things that annoy me in my Christian walk:
The rather annoying, judgmental, and uncharitable practice of some lay Catholics to impose their personal interpretation of Church teaching on others in wide-sweeping, blanket generalizations, while ignoring situational variables.
Often done in a mean-spirited, high-handed, and sanctimonious manner, these practices are neither Christian, nor are they helpful. Some situations are best handled in consultation with competent medical doctors and spiritual advisors. These uncharitable practices cause the greater sin of driving away potential converts and soiling the reputation of the Church.
Too often, we see creeping legalism and arrogance regarding Church doctrine from the incompetent and uninformed. Hypocritical observance of the letter of religious or moral law without regard for the spirit is the very definition of anti-Christ.