After the death of Harsha Vardhana, the power in Kanyakubja was usurped by Arunashva. Let`s analyze the other options for a better understanding:

Option 1: Adityasena - There is no historical evidence or context provided to suggest that Adityasena usurped power in Kanyakubja after Harsha Vardhana`s death.

Option 3: Shashanka - Shashanka was a powerful king of Gauda (Bengal) during the 7th century. He ruled independently and was not involved in the usurpation of power in Kanyakubja.

Option 4: Lalitaditya - Lalitaditya was a famous ruler of the Karkota dynasty in Kashmir during the 8th century. He did not have any historical connection to Kanyakubja or the power struggle after Harsha Vardhana`s death.

Based on the options provided, option 2, Arunashva, is the most viable answer. However, it is important to note that historical events can be complex, and without additional context, there may be other possible answers or scenarios.