Jack Johnson seemed stupidly good at this, even when outweighed 20 pounds by Jeffries. He was bending Jeffries arms behind his back.
great post, as far as effective punching in a clinch, the best fighter that i have ever seen as far as clinch control and effectiveness is bernard hopkins, he actually "hurts" his opponents in the clinch (meaning that they buckle or become wobbled) duran and hagler where great too and one guy that i thought was very unlikely but very good in a clinch is pernell whitaker.
Duran was amazing in the clinch. He'd just close in, put his head in your chest and break you down. And he didn't have to hit and hold, tie you up and then punch on his way out... He just closed the gap and tore people apart on the inside and they couldn't retaliate... No idea how he did it.
How about Chavez? I don't recall him being that easy to clinch, and I recall seeing him elbow out of attempts many times. I don't mean an illegal elbow strike, I mean blocking the attempted clinch by spreading his elbows wide. Stopping your opponent from clinching has to be an important part of clinch control.
Not sure, honestly. It was on a show called "Tyson's Heavyweight Rivals" where he evaluated how he felt classic fighters would do against him alongside some other guy. He was in awe of Johnson's strength and commented on the arm bending as the segment of it was played.