Enjoyment from watching others get hurt, and sociopathy

[Angrboda]

A lot of times the violence occurs within a contextualized relationship in which we in some sense think it's okay for the violence to occur. Sports for example, are often seen as a symbolic reenactment of our warlike selves, in which we objectify and victimize the "other" in the context of battle between two sides. We root for the player on our team that makes the aggressive hit, but we cringe when "our own" player takes a significant hit. In other circumstances, it's contextualized by the victim having done or said something to make them "deserving" of the violence, as a sort of justice. We notice this a lot in crime dramas in which the bad guy usually "gets what's coming to him." In other circumstances, the violence is contextualized as a predator-prey relationship, such as the roadrunner and coyote, or tom and jerry, or bugs bunny and elmer fudd; it's odd that in those relationships, the results of the violence are inverted in order to make the predator into the bad guy. But the inter-species violence between the characters is normal and expected.

So I think a lot of the violence described by the OP is actually normalized by the relationship of the victim to the victimizer in a lot of circumstances, rather than by any inherent sociopathic tendencies in the viewer. The real puzzling incidence is when we enjoy schadenfreude over the misfortune of a complete stranger. Even then, this is often enhanced in representations by the victim having done or said something beforehand which identifies them as a "bad" person.