Boxer Sergey Kovalev agreed to a $650k settlement with the woman he allegedly beat up in 2018 -- but the woman claims he failed to come up with the cash ... and now she's suing.
TMZ Sports broke the story ... the 36-year-old Russian superstar was accused of bashing Jamie Frontz in the face during a June 2018 attack in Big Bear, CA -- breaking her nose in the process.
Frontz told police she had rejected Kovalev's romantic advances earlier in the night and he followed her back to her cabin to make her pay. Frontz claims the former light heavyweight champ punched square in the face and she suffered a concussion and a displaced disk in her back as a result. She also claims "Krusher" brutalized her dog.
Kovalev was investigated by police and charged with felony assault, though he's since pled not guilty. If convicted, he faces up to 4 years in prison. That case is still pending.
Frontz had sued Kovalev for assault and battery demanding $8 MILLION -- but claims she agreed to drop the case after reaching a confidential settlement with the boxer.
The problem ... Frontz claims Kovalev hasn't lived up to his end of the bargain so she's exposing the terms of the secret deal in a NEW lawsuit.
According to the court docs, obtained by TMZ Sports, Frontz claims Kovalev agreed to fork over $650,000 in 3 easy installments ... but stopped paying after cutting the initial $250,000 check in October.
Frontz believes Kovalev should easily have the money -- claiming in her lawsuit he was guaranteed to make at least $10 MILLION from his Nov. fight against Canelo Alvarez.
Now, Frontz is suing for breach of contract -- and though she didn't specify an exact dollar amount, it's clear she wants MORE money than the original $650k deal to cover legal fees and punitive damages.
We've reached out to Kovalev for comment -- so far, no word back.