Did Andre Ward ruin fighters?

No.

 

He did Dawson's & Kovalev's.

 

The bottle had a whole lot more to do with what happened to Kovalev then anything Ward ever did.

 

He ruined their balls

 

I think that can certainly be said for Chad Dawson. That was a horrible beating and Chad never regained his status again.

 

He did ruin Kessler in away. Mikkel had issues with his eye(s?) from the headbutts and cuts He suffered in that fight, which forced him to pull out of Super Six tournament and derailed his caeer.
Chad Dawson was also never the same - although He never should've dropped to 168 at that stage of his career

Guys like Froch or Bika on the other hand had their biggest career wins after losing to Ward. Kovalev had some solid wins moving forward also, then He just got old probably. Ward probably ruined his "Krusher" mystique, though.

 

you could argue the significant weight-cut has more to do as well for Dawson since his punch resistance completely disappeared

 

A case certainly could be made for Dawson. As has been said, Kovalev had other issues and also had some decent wins afterwards, but I still think it's very clear that his confidence wasn't the same as in the first fight. When Ward started to get into it in the rematch after losing the first three rounds it was clear to see that the will to fight was gradually fading out of Kovalev.

 

I'd suggest there's a bigger case for the scales having ruined Dawson.

 

You mean that making a big cut for one fight ruined him for ever after? I don't think one cut has that effect, can't come to think of any case where it has. Guess you could argue RJJ, but I think that only effected him in the first fight against Tarver, not the second.

 

If one led to the defeat that, in turn, led to his ruination - then, yes.

 

But why would he be so badly effected by the defeat if he knew it only had to do with the cut?

 

In what way does having a reasoned rationale for why he'd just had the ever living **** beaten out of him help lessen the impact of that beating?