Responsible, being required to answer for one's own actions. It's sometimes used with a moral connotation meaning morally required to be responsible for one's actions without specifying to whom one is accountable.

More often, the term accountable is used to describe the sociological fact that a person or organisation in question is required to answer to a particular party by some rules or organisational structure. For example, the statement "the principal is accountable to the school board" gives a description of the social facts without suggesting anything about the ethical legitimacy of the organisational structure.