Is it permissible to lighten (with dye) or pluck an eyebrow that has a defect (such as a scar where hair does not grow) in order to unify the shape of the two eyebrows, and which is better in Islamic law in this case, plucking or lightening?

The basic ruling for plucking eyebrows is that it is forbidden, due to the Prophet's (peace be upon him) saying: "Allah has cursed the tattooers and those who get tattooed, the eyebrow pluckers and those who get their eyebrows plucked, and those who create spaces between their teeth for beauty, altering the creation of Allah." However, it is permissible to take from the eyebrows in two situations: necessity for treatment, or if the eyebrow hair is excessively long to an extent that is harmful or disfigures one's appearance, reaching the point of disfigurement. As for bleaching the eyebrows, it is not forbidden, because it is neither plucking nor does it carry its meaning. It is preferable to plucking, which is originally forbidden except for what has been exempted.