This morning he SPAT on the carpet and has leathered his older brother with a light sabre. 
Telling him off doesn't work, as he either laughs or gets aggressive. Sticker charts don't work, confiscating things doesn't work because he doesn't care enough about anything. Time out doesn't work because he won't stay, so we've recently been putting him in the conservatory (which locks) because it's the only way we can make him leave his brother alone for 5 minutes.
Am at a total loss, I just end up ignoring him but I know that's not great either. Feels like he gets away with murder. Is there anything I can do that I've not tried? I sometimes wonder if he's got some sort of behavioural problem but other times he can be so angelic you'd think butter wouldn't melt.