We’re there at the moment too! 14 yo, had a total personality bypass, has literally changed into stereotypical teen overnight, and lost all sense of respect and what’s right and what’s wrong. Again, absolutely no remorse shown from my cherub DS either.
He’s not quiet at losing the rag stage, so not too much slamming and banging of doors, and I haven’t had too many Hate You/Wish You Were Dead pleasantries from him, but maybe that will come in due course.
I think I’m struggling with the transition more than he is, which is crazy seems as my job is working with teenagers (albeit older, 16 - 21), but it’s so different when it’s your own flesh and blood morphing into this young adult with a mind and language of their own.
I would just continue to point out that his behaviour and the disrespect isn’t acceptable, and continue with the removal of phone/Xbox/thing if he oversteps the mark.
As I say to my work teens every single day, action and consequences, kiddos!
This really is just a phase. Try not to lose sight that it will be over and it’s not forever. Correct when needed, pick your arguments, walk away and ignore if it doesn’t warrant your blood pressure going through the roof. I was an A1 shite to my mum growing up; how she survived I don’t know, but she did, we did, and I’m actually a Very Nice Person now, with a great relationship with me Mum! This too shall pass.