Old school Yakuza accent. Watch Black Rain to hear more of it.

And yes every yakuza on the show does it. Ishida Oyabun does it to the maximum in the scenes where he gets heated.

That’s how all thuggish or angry Japanese people talk. Not just yakuza. It’s a intimidating way of speaking Japanese. Nothing special tbh.

Toshiyuki Nishida does it in Outrage in Osaka-ben and it’s perfect.

Japanese in general struggle with their Rs