Yeah Pride FC was UFC's biggest competition that was founded in 1997. Zuffa (the parent company of UFC) bought Pride back in 2007.
There are lots of fighters that came from Pride. From IronMan's rankings these are some of the ones that came famous in Pride:
Antonio Rodrigo Nogueira
Mauricio Shogun Rua
Antonio Rogerio Nogueira
Quinton Rampage Jackson
Please tell me which are missing
And these are the fighters that are in the list and have fought in Pride:
Dan Henderson (I wasnt sure where to put him)
Yushin Okami (fought only twice)
And these wasnt on the list but was succesful in Pride and fights now in the UFC.
Mirko Cro Cop
Mark Coleman (got fired)
Sry i ran out of time please tell me which are missing