This paper aims to advance a theoretical and clinical perspective on the developmental origin and role of omnipotence in early object relations, and a differentiation of the adult sequelae of these maturational dynamics. The focus is on negative omnipotence as inherent in the constitution and impact of the psychotic part of the personality. The case history of the psychoanalytic psychotherapy of a man with a psychiatric diagnosis of obsessive-compulsive disorder illustrates the self and treatment defeating impact of negative omnipotence. Diplomatic therapeutic engagement, based on the understanding that these negative therapeutic dynamics represent unfinished maturational processes, is presented as enabling treatment to progress and facilitate gradual beneficial modification in the use of omnipotence intrapsychically and inter-personally.