The consensus in Legend seems to be that Chian is the absolute worst—even June and Metias don't like him when they're still buying the Republic's bag of lies. He's a cruel man who uses his position of power in the Republic inflict pain on others:
Then I remembered that Chian had mentored Metias before he joined Commander Jameson's squad. Metias hated him. (1.6.15)
Chian is a cruel, conniving man who likes to see other people die and suffer. He runs the Trials and is the person who sent Day off to be experimented on. He even told Metias to kill a little girl who was trying to escape from her Trial. For a man like Chian, power is a means to giving into his baser instincts.