It's not single acts, it's a pattern of behaviour which starts slowly and gradually escalates. Key indicators would be if one partner is afraid of the other, or feels that all the time he/she must moderate his/her behaviour because of how the other will react. A particular red flag is if one person becomes very visibly angry/agressive at not getting his/her own way, yet blames the other partner for not obeying or submitting or moderating his/her behaviour.
I think perhaps the main factor with abusers is that they feel that they are the important partner in the relationship, that the other partner should indulge them, placate them, service them and not contradict them in any way.