can 1 loss ruin your career im particularly talkin about the heavyweight division

I think it's easier in the HW division at the moment, with the lack of quality opposition it means guys like Sam Peter get to fight Wlad twice and Vitali after multiple losses, Tony Thompson has had two shots against Wlad, Chambers lost against Povetkin and then ended up fighting Wlad. Hasim Rahman has had a plenty of title shots. I think the HW division is especially forgiving actually, Wlad has 3 losses and climbed back to the top, Lennox, Ali, Vitali, Louis all have losses and got to the top of the sport.

Often it does ruin a fighters career. Remember most of it is mental and when a fighter's confidence is shattered, it is hard putting the pieces back together. Sometimes they do but I believe it usually takes time. Seems the most common mistake they make is rushing that process and end up never getting back to where they once were. For the ones that do put the pieces back together, perhaps it takes a strong resolve and desire that many unfortunitely don't possess.

The fans usually think a fighter is finished after a loss, but in most cases he isn't. It's actually one of the things I hate most about boxing. No one says Roger Federer is finished after he loses a match.

Naseem Hamed. He lost the will to fight after the Barrera loss.

Some fighters recover better, some don't. This goes throughout the divisions. Meldrick Taylor took a bad beating from J.C. Chavez, moved up in weight, had some success but wasn't what he had been. Fernando Vargas had even less success, post-Tito. David Reid did nothing of note after fighting Tito. Davey Moore did little of note after fighting Roberto Duran. Duran hit his peak years after his first loss. Lennox Lewis improved after his loss to Oliver McCall. Steward helped him with his balance issues and some technical flaws. You can see Lewis afterwards throw straight rights more often rather than those ugly winging right hands. Sonny Liston had an early loss in his career.

Ali ruined prime Foreman he was never the same after that.

Depends on the fighters mindset...champions fall and get up that's what separates them from the rest

HW's are the most powerful, so anybody can go anytime it's easier for them to recover from a loss but 1 loss can wreck a career at any weight if it's too brutal Lacy is the best recent example guys like Miranda and Mayorga weren't the same after getting destroyed