He said his brother tattooed the nickname "Devast8" on his face during a heavy night of drinking in jail.
When released he wanted to get off the unemployment benefit, get a job and put food on the table for his family.
But he struggled, he said, because of the significant tattoo.
Cropp was scheduled to stand trial before a judge in both cases.
But on the day of each trial, he changed his pleas to guilty.
He appeared before Judge Anna Johns at Manukau today and will be sentenced on all charges together in May.
At Papakura he admitted charges of male assaults female and threatening to injure with intent to frighten.
His victim was 17 weeks pregnant at the time of the offending.
Judge Gerard Winter granted the Herald access to the court file so the case against Cropp could be reported in full.
On May 24 last year Cropp and the woman - who cannot be identified - argued over her cellphone.
He had demanded to see who she had been contacting.
When she refused Cropp said to her "you better shut the f**k up b***h or I'll punch your mouth in".
She replied "do it then, hasn't stopped you before".
Five days later the pair argued again.
This time they were in a car and Cropp was driving.
Again, he swore at the woman and she asked him to stop the car.
When he refused she opened the door in an attempt to get away from him.
Cropp grabbed her by the collar of her hoodie, twisting it around her neck so her breathing was restricted.
When they reached their destination Cropp kicked the woman in the knee.
He later told police he grabbed her hoodie to stop her getting out of the car in traffic.
Cropp, who appeared in court wearing a bumbag with the word Devast8 penned in block letters on the waist strap, tried to prevent the Herald from covering the case.
