Vanraj is a recurring antagonist on the show. However, it's hard to deduce the motives behind his actions toward the protagonists.
We know the following:
Vanraj apparently killed Shivani personally.
Vanraj, some of his friends, or both, kidnapped Aditi, and held her weeks, at minimum, but did not kill her.
Vanraj tried to kill Vikrant with the demonic book, but after failing, he didn't seem to try too hard again. Considering his supernatural strength, ability to teleport and become immaterial, telekinetic powers, and many other unpleasant abilities, he could probably have given a decent try.
At first I thought Vanraj simply wanted to kill people with the ability to see spirits, since they could be a threat, and that is why he targeted Shivani. However, the fact that he held Aditi hostage rather than killing her seems to dismiss that theory. One might also think that Vanraj wants to kill anyone who interferes with this business, but again, his not killing Aditi, and not continuing to target Vikrant while the latter was convalescing, make this seem implausible. Later we're told that
Shivani and Aditi are siblings, and that Vikrant is the one who can kill Vanraj.
But this doesn't clarify things, seemingly just giving more reasons for Vanraj to have killed Aditi when he had her captive, and to have pursued Vikrant more vigorously.
So what is behind Vanraj's actions? Is he just interested in random acts of unkindness without much care for consistency? (He is a demon, after all). Or is there some unifying thread behind when he tries to kill someone and when he doesn't?