Is a person held accountable for the anger that drives him to disbelief, uttering obscene words, and imagining sexual fantasies?

If the thoughts are mere waswas (whispers/insinuations), then pay no attention to them and strive against them. They will not harm you as long as you detest them. However, if you utter disbelief by your own choice, this is apostasy that necessitates repentance. As for imaginations, there is no sin upon you if they overwhelm you. But if you summon them and indulge in them by your own choice, then there is a concern of sin upon you, and you ought to guard your thoughts.