When it comes to the USA, I've come across bigger and more serious busts regarding the Outlaws than the Hells Angels tbh.

Even in that fairly recent Indiana bust with Frank Wheeler, the crimes were reasonably diversified: narcotics, extortion, gambling, fraud, fencing...
During that "Cocaine Cowboy" era the Outlaws were moving tons and tons of dope from Central Florida and all over the South. Under Taco Bowman they must've made lots of money as well.

Could the area they operate in have something to do with this? In the USA the Outlaws seem to hold quite a bit of sway in the somewhat poorer and more rural parts of the South and the Midwest. Whereas the Hells Angels in the USA are based in the, by now, slightly more cosmopolitan parts where there might be less of a "gunslinger" thinking going on.

In terms of OMCG stuff I haven't come across more insane stories anywhere than those of the Hells Angels in Quebec (especially from the 70's to the 90's) or those of the Outlaws in the South during the 80's and 90's. Sure you can find biker stuff that's happening in other parts of the world, but rarely upper tier criminal activities coupled with violence on that scale.