Andy Hug and it's no where close in terms of technique and execution.
But in terms of success, it has to be Aerts (even though Hoost won 1 GP more than him, I still think his boxing is garbage).
I think for MMA, it has to be Mirko, he was pure talent before he lost his soul.
PS: Bakauw really isn't that good of a striker, he has insane kicks, but his boxing isn't too great. Someone like Masato or Sauwer is much much more well rounded than him.