The new Viber managing tool for groups let the group admin remove a person/contact/participants from a specific Viber group. To remove a contact from Viber group, do as follows:
1. Open Viber on your Android device (make sure you are running the latest Viber version)
2. Open the group you'd like to remove a specific person from
3. From the right edge, swipe left to open the sidebar menu
4. In the list of participants, tap the contact/person/number you want to remove from the group
5. Touch the Remove from chat option and you are all done
Note that, in order to remove a person from Viber group, you must be selected as that Viber group.