A "deliberate act" refers to something that is done on purpose or with intention. It means that the person or people involved carefully thought about what they were doing and made a conscious decision to carry it out. Full definition
In other cases, the abusive behavior may occur with no emotion: a quiet, deliberate act of harm used by a teen to maintain power over a parent. (empoweringparents.com)
That's because data security breaches aren't always the result of deliberate acts by malicious external actors. (elearningindustry.com)