I think 'frank and fearless' is likely to be way more constructive than 'brutal'. If you have a group of people in a room, all pointing out shortcomings in someones code it is pretty inevitable that they are going to get defensive, especially if they haven't had a chance to think about the criticism ahead of time. Code reviews are probably going to be more productive if you comment code ahead of time and give the person a chance to think about it before discussing it with them one on one. You can always bring in others if you can't agree. I suppose the format needs to be informed by the personalities of those involved.