Who do you think? I think it's actually super close between the top 4 (imo) of Tszyu, Kovalev, Beterbiev & Bivol.
Probably going to be Bivol when all is said and done Not 100% he's the best, but he still has time to add to an already very good resume
Prime Kovalev it was something... I like Povetkin and Lebedev but they are controversial for use some doping. Archachakov marked me more than others specially for his charism "the last Soviet boxer" so I will vote for him.
Ibrahimov is probably the worst on the list high potential but so boring and a short career when we never really see his limits..
I voted for Kovalev - partly out of sentiment as I enjoyed watching him so much. But at his peak he was an absolute monster. his peak was very short lived due to his discipline issues - but peak for peak and pound for pound I would take him over Bivol anytime.
Facts if we include mma and I'm tempted to put khabib after him, although he did retire too early which weakens resume