Who would beat Golovkin at MW, past or present?

We'll keep this to the modern-ish era otherwise it opens a can of worms about athleticism, old fighters fighting cans, old fighters having more competition... where does it end? This is a game of probabilities, GGG is a top operator but would anybody be outraged by the suggestion that he loses (or sometimes loses) to:

Hagler
SRR
Hearns
SRL
RJJ
Hopkins
Toney
Canelo
McCallum
Collins
Eubank
Watson
Monzon
Jermain Taylor
Benn
Pirog - might seem like a strange pick but before his injury he would have taken over the division and maybe beyond
If Calzaghe or Ward fought at 160 he'd be in trouble, and he'd be massacred at 168 by them.
Froch, Pavlik and Kessler give him hell at 168.

I'm not having it that he's this all time H2H monster who runs through everybody, when he barely overcame Jacobs and Derevyanchenko and couldn't stamp his authority on Canelo. GGG should have concentrated on fighting the best available at all times, rather than daft fights against Steve Rolls, Szeremeta, Martirosyan (3 of his last 5 fights!), dragging Kell Brook up rather than making good on his promise of 154-168 which didn't actually happen, Dominic Wade, Willie Monroe Jr, and who the fu ck knows he fought on his way up... it would have sharpened his game. His amateur career went on for far too long too.

As an olive branch, GGG is competitive against many of those guys but we can't elevate him above them based on what he's actually done. Knocking over some B fighters at middleweight, his only weight, doesn't cut the ice.

You know, Tom Loeffler and Abel Sanchez have a lot to answer for. They ruined a potential top 50 ATG here.