>>213843530 (OP)
He’s a violent psychopath who often is wasted and has next to no impulse control.
The only reason he doesn’t beat up Rent Boy and co. every time he sees them is because he actually knew and grew up with Rent Boy since they were wee lads a l and that has created this weird notion of loyalty/attachment that makes him think they are all good mates even though in reality most of them are just terrified of Franco and humour him because it’s safer to be on his good side and risk being wrecked by him.
I think in the book it’s even mentioned how Renton when he was a teen and still in school stumbles into Begbie by accident and he’s all “oh fuck, I thought I was free of this guy”.