OP you sound very bitter towards your brother, unfortunately that won't help the situation at all, in fact it will only make it worse.
I notice you mention your Mum a few times - what about Dad?
Your parents must take some responsibility for the situation. At some point your brother was a teen, a child and I'm guessing that he was given a game console and then NOT given boundaries for ir...
I have a 14 year old son, his xbox is not in his room, its downstairs in a communal room and I've always put rules in place about how long he games for before taking a break and he's never been allowed to play games that are PEGI rated above his age - not Fortnite til he was over 12 and definitely no COD, GTA (ever hopefully) unlike many of his peers who have consoles in bedrooms & are up till all hours.
I get so sick of 'oh well, what can you do' parenting - YOU'RE the parent! It's literally your job to parent and that includes setting boundaries and good examples.
Secondly, I suspect that your brother is possibly neurodivergent and almost certainly has unaddressed mental health needs and the more you threaten and bully him, the more he'll be backed into a corner.
You it seems, are not suffering as your brother is and as tough as it is, if you want the situation to be different, it's you that's going to have to change first.
You're going to have to try and see the world through your brothers eyes, understand how he feels and try and work in a different way.
You catch more flies with honey than vinegar ... remember that.