Here is a list of some sample character traits that may be applicable for the main character in your book analysis (Note- the traits can be phrased in the noun or adjective form in the thesis statement i.e. brave/bravery, vengefulness/vengeful) Some of the traits given below may be in the noun or adjective form. Additionally, this list is not exhaustive.
Bravery, humility, piety, fortitude, resourcefulness/ cleverness, intelligence, kindness/compassion/ generosity, cold-heartedness, forgiveness, ill-tempered, proud, ambition, stubbornness, hard-working, reliable, mysterious/elusive, observant, selfless, just, wise, introverted, idealistic, cowardly, self-centered, insecure, immature.
Be careful when using the traits of loyalty and determination/perseverance. Almost any character (whether good or evil) is loyal to something, to themselves or others. In addition, every main character is going to have some level of determination because they are the protagonist; the story does not progress if they simply give up or fail to move forward. Therefore, declaring that the main character is loyal or determined can be generic and not specific to that character, almost using these traits as an everyman stand-in trait. This does not mean some characters are not distinctly loyal or determined. It does mean, however, that you should use caution and make sure the character has these traits in a specific, strong way.