Simply create a readonly user in security/file.xml,
<record id="group_readonly_user" model="res.groups">
<field name="name">Readonly</field>
<!-- Place other tags -->
</record>
Then in security/ir.model.access.csv grant the read access for this group,
ID,Name,Model Name,Module Name, read,write,create,delete
access_hr_employee,hr.employee,model_hr_employee,hr.group_readonly_user,1,0,0,0
access_hr_attendance,hr.attendance,model_hr_attendance,hr.group_readonly_user,1,0,0,0
.
.
#Do the same thing for all the models/tables you want to make them readonly for this specific group
Then create your user "ABC User" and assign this group for him/her.
Check this module : https://apps.odoo.com/apps/modules/10.0/read_only_user/