1) Means good but not publicized as much as other stuff,opposite of overrated.
2) Something that is better than most people think it is.
3) Something or someone not well known by the mass public but of high quality.
–verb (used with object), -rat⋅ed, -rat⋅ing.
to rate or evaluate too low; underestimate.
1615–25; under- + rate 1
Theses are all definitions of UNDERRATED and they all apply to the top six fighters that everyone rates too low. These fighters have either not received enough attention, talk too much, fight with a boring style, or just stay on the blind side of most fans.
Enjoy the Most Underrated Fighters.