The worse case scenario would involve an unwanted child coming into this world in the absence of love and affection. This is a child who will not only fail to thrive, but might die a premature death during Childhood.
Poor parenting might include a measure of love and affection, but will too often fail to leave the child feeling that those needs are being adequately satisfied. Parental neglect and/or authoritarian parenting practices (invariably including spanking as a punishment) are the major causes of parents failing to meet the emotional needs of their children to feel loved and accepted.
Show me a child who has been failed in having their emotional needs adequately satisfied, and I’ll show you a child who is prone to missing out on a healthy process of emotional growth and development. The negative consequences are myriad and can range from sociopathy/psychopathy to inadequate empathy, to anger issues, to low self-esteem, to clinical depression, to criminal behavior, to homelessness, or, simply, to a miserable existence.
The degree of long-term harm caused by poor parenting is dependent on the degree of unsatisfied emotional need the child has suffered.
I’ve worked with kids who felt their parent/s could not have really loved them based on the way they were treated, but experienced rich nurturing from other sources, such as relatives, or nannies. These were the kids who made the best candidates to overcome the poor parenting they had suffered.
True enough, many of us have overcome poor parenting to the extent that we can get by in the world, or even live a happy life. But, sadly, there are many others of us who are never provided the opportunity to overcome the harm suffered.