Adjective
divisive - Causing disagreement or hostility between people, tending to disrupt unity or harmony.
The election was fought over the deeply divisive issue of immigration, and people on either side of the issue can't see things from the other point of view.
premeditated - Done with prior thought or preparation; thought out or planned in advance, often with careful consideration or intention.
The detective revealed that the crime was premeditated, with evidence showing the suspect had planned it for weeks.