The UFC has 3 acknowledged fixed fights in it's history with evidence:
- Oleg Taktarov vs. Anthony Macias - (Big John McCarthy's book "Let's Bring It On")
- Don Frye vs. Mark Hall 3 - (Frye said it himself in an interview)
- Leo Kuntz vs. Tae Hyun Bang - (Tae Hyun Bang went to fucking jail because of it lol)
In comparison PRIDE has one proven fixed fight in it's history, Nobuhiko Takada vs Mark Coleman. That fight took place in 1999, the era where every organization had fixed fights... including the UFC
Meanwhile the UFC has a proven fixed fight in 2015.
There are also multiple other UFC fights that are suspicious but without evidence. Frank Shamrock vs Rich Franklin, as just one example. Frank took part in a few works in Pancase so it's not exactly a huge leap considering he literally faked being punched and then dropped to the ground before ever being touched.