My definition of underrated would be:-
1. Having the physique to win competitions, but never doing so/taking a long time to win, e.g. winning the top amateur competitions to turn pro. Example of this are:-
Annie Rivieccio - she should've won the HW & overall North Americans/USAs many times over the years. Never seemed to be in favour with the judges (why?) until almost at the end of her career, so she didn't have time to "bed in" as a pro and go on to greater things;
Lora Ottenad (like Annie, always the bridesmaid, [finishing 3rd - 6th annually], never the bride until near the end of her career - again too late to make an impact as a pro)
2. Being short, but having a great physique, but not standing a chance up against the taller women. Examples:-
Andrulla Blanchette (should've won/done better at pro shows than her shared one-time "win" at the 2000 Ms O. [when not up against Iris at her best directly/Lenda/Kim - separate LW & HW] - almost always got over looked when up against the taller/bigger pros)
Zuzana Korinkova (never seen a better ripped FBB still carrying a decent amount of muscle [for her height/stature])
Sue Price (stunning, great physique)
3. Being too tall/big (5' 4" - 5' 7" & 140 - 160lbs seems to be the most favoured range for the judges):-
Lora Ottenad again (5' 8" or so - big, shapely, well conditioned and still good looking facially at contest time. Of course, added to that, that low, sexy voice and reputation [negative from a judging standpoint?] for her sexy "session" videos [you know - THAT clip of her "humping" the guy after wrestling him - my all-time fave short clip - never seen the whole video])
4. Others (not already listed):-
Lisa Bavington (my kinda FBB - she had the looks, femininity, size, conditioning and shape - a GREAT advertisement for the sport back in the late 1990s)
Vicki Gates (should've won more, including [at least] the joint 2000 Ms O. when beaten by Valentina Chepigain the HW category)
As has been said, I'm sure there are more....