Definitely Mike Tyson for me. I've seen all but a handful of his fights...there are probably no more than 3 or 4 of his fights I haven't seen. De La Hoya is another one. I've followed him since Barcelona. I've seen probably about 70% of his fights.
seen eveyr cotto fight(not all of them live obviously). seen every trindad, whitaker, and jones fight. look to see the whole library of the classics though(sugar ray robinson, ali, tyson, etc).
i usually get into these moods where im addicted to watching a certain fighter for a certain period of time currently im on a hagler buzz over all ive probably watched more trinidad, morales, corrales, gatti, barrera and arguello than any other fighters
Ironically, it's Mayweather. I actually just bought all of his fights on DVD for $15.00 on eBay. Pacquiao is runner up.
Too many to mention. Tyson(all fights), Ali, Hearns(all fights), Leonard, Mayweather(all fights), Pacquiao(all fights), Cotto(all fights), Morales(all fights), RJJ(all fights), DLH, Hopkins, Lacy(all fights), Marquez, Barrera, Mosley(all fights), Holyfield, Bowe, Foreman, Adamek(all fights), Golota, Trinidad and whoever else I'm forgetting.
I've got so many career sets I can't really say. Not all of them are 100% complete but most are. I am certain I have got hold of every fight recorded by the many fighters I'm a big fan of.