Nate Clements, Fred Smoot, Champ Bailey, Ty Law, Charles Woodson, Dunta Robinson, Chris McCallister, Lito Shepard, Samari Rolle, D'Angelo Hall, Antoine Winfield. Cases could be made for Asamougha from the Raiders and Pacman Jones from the Titans as well, though they are probably even or a step behind Samuel.
Asante is NOT a strong tackler. Its hit or miss as to whether he wraps up. He relies on his hitting ability to knock players off their feet. I feel he's not great in press coverage and its one reason why the Pats play a ZONE coverage. Asante doesn't go up and out-muscle WRs very often. He times things so that he gets the interception clean, but if he misses, the WR is gone.
Teams are NOT afraid of Samuel. Its why they go after him so often.
Also, Samuel has benefitted, majorly, from the pressure that the Pats Pass Rush puts on. At least 5 of the Ints that Asante made were on "DUCKS" (floaters because of the pass rush) to his side of the field.