In order to assess whether or not both are tragic characters, initially it's imperative to analyze their conflictive values. Creons character attaches importance to the state and his own law rather than anything else, whereas Antigones appears to put family first and foremost. Sophocles' use of soliloquy accentuates this:
Antigone: He is my brother and- deny it a you will-
your brother too.
No one will ever convict me for a traitor.
Conversely, Creon has very different ideals:
Creon: And whoever places a friend
above the good of his own country, he is nothing
These quotes clearly highlight the distorted values Sophocles assigned Creon, who, as can be deduced from his words, is extremely power hungry and insensitive, whereas Antigone is perhaps ruled by her rebellious nature to oppose Creon completely. A confliction of these two values can be named a tragedy, therefore can the two heroes be called tragic'. This can also link back to the major theme of man-against the state, where Antigone goes against Creon because of diverse beliefs.
Nevertheless, in order to have two tragic characters it is crucial to assess whether they possess similar traits. Seemingly, Sophocles gave Creon and Antigone alike characters, emphasized through use of diction. For example both are very stubborn and seek glory: