When he was first introduced, Zackly was said to be a strict military leader who was only concerned with the best interests of humanity. As the head of the entire military, his priorities were said to lie within what is best for all of humanity. Only after being logically convinced of Eren's usefulness did he pardon him. At this time he appeared to take most things lightly, as if he had experienced them previously. During the trial of Eren, he wore simple clothes and conducted the trial without any drama or passion. Similarly, he overthrew the monarchy with an incredibly casual demeanor. This indicates that Zackly had no time for drama and was solely focused on carrying out his judgments. He remained ever serious but at the same time appeared tired as if his age was catching up to him. According to Armin, Zackly was among the people capable of abandoning their humanity to outdo the Titans as well as having the guts to also abandon things important to them in order to change something in the world, along with Erwin Smith, Ian Dietrich, and Dot Pixis. However, after Zackly assisted in the revolution against the monarchy he shows a completely different personality. He noted to Erwin that his only interest in participating was due to an intense and long-standing hatred of those in charge. He took great delight in seeing their fear when they fell from power. In direct contrast to the idea that he acted in the best interest of humanity, he told Erwin that he did not care if the revolution helps humanity or not. His only interest was his own desire to humiliate the monarchy, such that he set up a torture machine that fed one of them their own feces and called it a beautiful work of art, showing a demented and sociopathic side to him. Ultimately, he was willing to admit that he valued his own life more than humanity.