Despite herculean efforts by friends and family and even strangers, he is fundamentally broken in ways nobody seems to understand. He still largely thinks of himself as the person he was prior to the TBI.
My guess at this grim stage is the mechanisms are broken that allow him to self-correct his behavior and make accurate, up-to-date "I am" statements. Clues to this are when you confront him about his behavior or how he never bathes. He is not offended or worried but rather agitated, as if his brain short-circuits. At best you get cognitive distortions and at worst he storms away in a rage he won't remember five minutes later. Interventions and threats have no postive effect.
He will talk your ear off all day about hobbies he had prior to his TBI, and if you didn't smell him or notice his pan handling sign, you might not know there is any problem. But make no mistake, invite this man to live with you and you will be tearing your hair out after two weeks and kicking him out in three, if not sooner.
Every TBI is unique just as every person is. My relative does not accurately remember what parts of his brain was injured, so interviewing him would not yield much. Besides that, after this happened I read that something like 80% of TBIs do not even show on common medical imaging devices. In my relative's case there was evidence "suggestive" of DAI (diffuse axonal injury) which may explain why his deficits are so profound, but nobody can say. During therapy there was clear evidence that his deductive reasoning skills were seriously compromised, so imagine practical consequences if you cannot do simple deductive reasoning but also cannot realize it.
Then of course TBI survivors are many times more likely to suffer additional TBIs. Add substance abuse and limited to no impulse control and you have a person who is a danger to himself and often society, but who also may refuse to get the level of help they truly need. In his case, he needs assisted living including someone to manage all of his money, but in his mind he does not and he appears ready to fight it until his last breath.
I hope studies like this lead to more humane and informed programs to help people like him. I was just thinking this morning how unjust it is that murderers and other criminals can get room and board for life yet the best we can manage for this once talented and caring member of society is a room in a drug-infested flop house that costs half of his disability income.