A parent should always evaluate if they are spanking their child out of anger or yelling excessively at their child (and ends up feeling bad after, because they realize they were wrong) should go for help before everlasting damage is done to their child. It doesn’t mean the parent is bad, rather it may be because of abuse in their own upbringing, their own shame, or their current circumstances that are causing them to be stressed or overwhelmed.
The child should not have to suffer. Go for help. You won’t regret it. If you don’t go for help, you may regret it big time.