Final answer:
Instrumental aggression is an aggressive act needed to achieve an objective without the intent to cause pain, distinct from hostile aggression.
Step-by-step explanation:
The term that fits the definition provided of an aggressive act committed by any person which does not amount to an assault and is necessary to accomplish one's objective is instrumental aggression. Unlike hostile aggression, which is driven by anger and the intent to cause pain, instrumental aggression is motivated by the desire to achieve a specific goal and does not inherently involve the intent to cause pain. For instance, in cases of self-defense, one might use force to protect themselves, aligning with the concept of defensive force. This form of aggression can be seen as a means to an end, and in some philosophical or legal frameworks, it might be justified as long as it is proportionate and necessary to achieve the lawful objective.