Heavyweights who were specifically vulnerable to the left hook?

Now that you mention Foreman…
On second thought Jamaica George Could be the possible exception; although his "invulnerability" to Joe's left hook was because George made dang sure to stay the heck out of range taking advantage of the huge gap in reach with his jabbing and, particularly, with his borderline illegal pushing...

 

Yeah, and even describing it as borderline might be generous.

Not a lot of time or opportunity for Joe to land significantly but before Foreman did ramp up the push/shove, Joe did catch him with a nice left hook which would’ve made Foreman that much more careful to stay clear thereafter.

In their rematch that lasted longer, Frazier cleanly landed several whistling hooks but Foreman took them well.

 

As a disclaimer: Ali’s record/performances in the AMs, particularly at just 15 yo vs an 18 yo, hold little to no weight or importance next to his pro record.

Still, I wondered if his stoppage at the hands of 6’4” Kent Green in ‘57 involved the left hook in any way, shape or form.

As far I have read, it was a right hand that initially wobbled young Ali and basically a two fisted attack thereafter that forced the stoppage.

It seems Green held his stoppage victory over Ali in the AMs in due proportion and context.

There were promotional talks of his rematching Ali as a pro in the later 60s and even talk years later in the late 70s of them putting on an exhibition match which never came to fruition.

 

Now that you mention it, George Jones also dropped Ali in the amateurs with his "tire iron" left hook. But Jones specialized with the left hook to the point where he was accused of being a one-handed fighter well into his pro career, so maybe we shouldn't read much into it.

 

Ali is happy to acknowledge all the other KDs he was subjected to during his am/pro career from absolute go to whoa.

It speaks volumes he doesn’t ever mention the brutal KD suffered at the hands (or hand, as you aptly qualified) of Tire Iron. Possibly the earliest seismic recording of Ali’s kinfolk being shook in Africa.

 

probably because Ali had virtually no head movement with his jab and usually kept his right hand pretty low when throwing it, his technique was actually pretty bad, he relied on his speed and timing but generally left himself open should the jab be slipped by someone like Frazier coming in, and by the time he fought Frazier he wasn't quite as quick on his feet

 

Good points. Imagine facing a boxer like Joe who was among, if not the, greatest exponent of the very punch you were most vulnerable to?

Like the pieces to a jigsaw that you wouldn’t want to fit so perfectly. Joe sure did find a home for his left hook on Ali’s chin.