Fortress Maximus is huge and powerful Autobot with few other Transformers matching his size or power. Despite this he is a pacifist and a reluctant warrior. His high status in the Autobot ranks often see's him take command of troops in battle and even take full command of the Autobots in the absence of their leader.
Being a Headmaster he is binary bonded to the Autobot, Cerebros, who forms his head in robot mode. He has also been binary bonded to the former Nebulon leader, Galen, and the human, Spike Witwicky.
Fortress Maximus has a very different personality in the IDW universe. Ignoring his pacifist nature established in the Marvel continuity, Maximus was a prison warden of an Autobot-run penitentiary where he repeatedly threatened to kill the prisoners.