What are alignment infractions? How are they handled?
At times, PCs may act out of synch with their alignments. In cases where the actions are particularly severe, or follow a trend of behavior of this sort, staff may choose to reset a character's alignment. There is no set 'alignment points' formula used by staff to determine alignment shifts. The rule of thumb used is this: It is always easier to slide downhill than climb uphill. Shifting toward the good or lawful ends of the axis is far more difficult than shifting down toward the evil or chaotic ends. Several PCs on the grid have done a goodly number of altruistic things who are morally neutral in alignment.
Note that alignment defines 'a character's or creature's general moral and personal attitudes,' which means that intentions and deeds are both important. However, there are many ways to react to a given situation. How your character acts in times when your moral and ethical fiber is tested is the best definition of his true alignment – anyone can behave in an admirable fashion in times of peace and prosperity.
In short: It is almost never one act that redeems you, though it may be one act that condemns you.
Look at it from this perspective: If someone murdered your child in cold blood, that person would be evil. How many good deeds would that person have to do to make up for that one cold-blooded murder? Could he ever do so?
Evil is a slippery slope, and one horrific act that shows a disregard for the life and welfare of others can send you hurtling downward. That cold-blooded baby killer is still evil, even if he thought the child was the Antichrist. Unless it is a fact that he did more good than harm with that act, it is an evil act.