Bruno Latour

One must read, that is also my favorite theory, is Bruno Latour's actor-network-theory. He extends what is considered an actor to non-human actors and even objects, to which he refers to as actants. He then argues that actors/actants can be viewed as combinations of its parts, which in turn are actors or actants, and further argues that these combinations are capable of more than its parts.

One example he provides is that a speedbump can be viewed as an actant-made police officer. Executing the will (enforcing the speed limit) of the police officer in absentia.

Another one is the human-gun-actor, which is an actor that comes into being through the relation of a human and a gun. Combined capable of more than its individual parts and thus irreducible in its actions to just one of its parts.

Randall Collins

IMO, the leading sociologist on violence. He argues that committing violence is actually very hard and that a confrontational tension has to be overcome to do so. He identified five relational processes through which this can be systematically be achieved, which are combinations of emotional mechanisms.

Anne Nassauer

Since we are on the topic of violence, I would like to point out Anne Nassauer, who, based on Collins' theory developed a set of relational processes to explain police brutality during protests. These processes lead to situational breakdowns, which are defined as the collapse of interactive routines between protesters and police, which heightens the tension between the actors and then releases itself in a moment of emotional superiority.