And those who harm believing men and believing women for [something] other than what they have earned have certainly born upon themselves a slander and manifest sin. (33:58)
This ayah is just describing and defining slander.
This verse determines the definition of slander. It is to ascribe a fault to a person which he does not have, or an error which he has not committed. The Holy Prophet also has explained it. According to Abu Da'ud and Tirmidhi, when he was asked as to what is ghibat (backbiting), he replied: 'It is to make mention of your brother in a manner derogatory to him. " The questioner said, "And if the fault is there in my brother?" . The Holy Prophet replied: `If the fault that you mentioned is there in him, you backbite him; if it is not there, you slandered him." Such an act is not only a moral sin, which will entail punishment in the Hereafter, but this verse also requires that in the law of an Islamic State also false allegation should be held as a culpable offense. (Maududi)
Allah is basically saying that harming a believer in any way (verbally, physically, etc.) for a sin he/she did not commit is slander and it is a great sin.
So, it is not the kind of harm that is slander (all harms are included), it is the circumstances that makes slander, namely when the victim doesn't deserve it because he did not commit anything wrong.