single punch (jab/lead/counter) Floyd Mayweather, by far combo artists, active fighters - Manny Pacquiao Andre Berto Yuriorkis Gamboa Amir Khan Shane Mosley honorary mention - Mike Tyson, early & prime - that d00d's punches were PHENOMENALLY fast! Both single and flurries were sometimes faster than some welterweights....
For best as in most damaging and hardest to avoid you can't go too far away from the number one fighter in the world today, Manny Pacquaio.