I’ve always heard Lanat is a type of Dua where we ask God to distance His mercy from someone. I fully believe in the concept of lanat as it is in the Quran and the ziyarats, but I’m wondering if this definition of lanat is correct?
The reason for my doubt is because in the case of ibn Muljum (as an example), even though we believe he was the worst person ever, as far is I know Imam Ali (a.s) showed him utmost mercy leading up to the incident and even after the incident. So on one hand we are asking God to distance His Mercy from ibn Muljum, but at the same time, our Imam never ceased showing him mercy. So unless I’m missing something, it seems our understanding of lanat leads to a type of contradiction? Which is why I’m thinking perhaps the definition of lanat must be something else?

1- Yes the definition of La’na is the withdrawal of mercy. It basically means we ask Allah to punish the evildoer for his evil.

2- Imam Ali (a) fought the evil doers and killed them. During the Prophet’s (s) life he killed many pagans. At Jamal, Siffin and Nahrawan he killed many. Sometimes evil doers must be fought because they want to spread their evil to others and endanger them. Justice means that they must be fought. They cannot always be forgiven in the name of mercy, because they’ll continue their aggression.

3- So then why did Imam Ali (a) show mercy to the one who struck him? Some possible reasons:

One: some people may have thought that Imam Ali had a personal problem with Ibn Muljam, and so they would have relegated his position from fighting to the truth to just having a person problem. Imam Ali did not want to give that impression. The way to do that is to treat his striker humanely.

Two: some people wanted to seek revenge, attack many people to avenge the death of Iman Ali, and cut Ibn Moljam to pieces. Imam Ali wanted to stop that, so he treated him this way. In his will to his son he said “make sure he isn’t dismembered and disfigured, for the Prophet banned that.”

Three: sometimes you want to show how vicious your enemy is. If Imam Ali had dealt with him roughly, some people may have felt bad for him, and the Imam didn’t want that. By treating him good, Imam Ali further showed just how evil his enemies were.