According to the report, the alleged victim identifies herself as Johnson's ex-girlfriend -- and told police he beat the crap out of her and strangled her early Friday morning until she blacked out in a hotel room after the two had been partying together in Vegas.

The GF told police ... while Johnson was strangling her, she told him, "If you are going to kill me squeeze harder and just do it." The GF says she then blacked out and lost consciousness.

As for why he attacked her in the first place, the woman told police Johnson became enraged after they were talking about his daughter ... and began to "beat her and throw her around the room."

According to the report, the GF told police she regained consciousness in a hotel hallway while just in her underwear and a see-through blouse and banged on doors until someone called for help.

Cops say the GF told police Johnson had attacked her multiple times in the past ... including a recent incident at the Wynn Hotel in Vegas.

According to the report, security made contact with Johnson and brought him to the security office.

One of the security guards told police ... while he was in the office, Johnson bragged about being released from charges "last time" ... and then told one of the guards that he was going to "rip your f*cking vocal cords out."

When cops arrived to the scene, officers noticed Johnson had a small cut on his cheek and one on his lip.