Re: twelvers
That sect was created after Iran was concured. Its main aim is to create disturbence among muslims.
They are involed in the murder of 3 khulfa-e rashdeen, Sayyedna Umer:razi:, Sayyedna Utham 
and Sayyedna Ali .
Yes, they created hatered among muslims by rumours and abusing khulfa. They accused Sayyedna Ali also because on the khilafat, he made an agreement with Mawiyah . Shia raised the issue that Imam is chosen from Allah and it i is only right of decendents for Sayyedna Ali (they say only to create disturbence, on the other hands, they have no love for them) so how Sayyedna Ali can make any other person
khalifa?