Absolute immunity is mostly a protection from civil lawsuits in personal capacity. When there is prosecutorial misconduct in a criminal case, defendants can get sanctions ranging to from dismissal with prejudice, mistrial, exclusion of evidence, to post-conviction relief depending on the severity of the misconduct. The biggest barriers are often either that the misconduct is hidden and difficult or impossible for the defendant (or really, his attorney) to discover, or that judges may decide that the misconduct was "harmless" and the defendant was not prejudiced, even in the face of blatant misconduct, when there is otherwise strong evidence.
As for the prosecutor themselves, defendants or judges can and do refer misconduct to bar associations which can and do disbar prosecutors. Judges can directly hold prosecutors in contempt and fine or jail them in extreme cases, or refer them for criminal prosecution on charges ranging from perjury, obstruction of justice, official misconduct, and criminal contempt and so on. As with any criminal cases involving criminal justice professionals, this is quite rare, but it does happen, and absolute immunity is no barrier to it.
As for the prosecutor themselves, defendants or judges can and do refer misconduct to bar associations which can and do disbar prosecutors. Judges can directly hold prosecutors in contempt and fine or jail them in extreme cases, or refer them for criminal prosecution on charges ranging from perjury, obstruction of justice, official misconduct, and criminal contempt and so on. As with any criminal cases involving criminal justice professionals, this is quite rare, but it does happen, and absolute immunity is no barrier to it.