Kant's approach to morality is extremely rational. According to Kant the main principle of morality is
the categorical imperative, which says that the maxims (principles) on which you act have to be such
that they can be universalised, ie that you can will them to become a universal law.
You might want to think about the consequences such a formalist approach has. E.g. an action could
be morally right according to Kant's theory but have terrible consequence. Also, and this is more
relevant to the contrast with character ethics, a person who follows Kant's rules might actually be a
very unpleasant person. E.g. they could lack any kind of sympathy or love for anyone, they may not
care about anyone's feelings, their actions might have horrible consequences, but they would still be
considered a (morally) good person by Kant. Would you want to call such a person good? Character
ethics is more about asking what makes someone a good person, and giving the answer not just in
terms of the rules they follow, but also the kind of person they are, the qualities of their character.
(And note that it may be difficult/ impossible to be a good person in this sense without doing at least
some of the actions that the categorical imperative would prescribe, but this would not be the only or
main thing that would count.)