Euan Walker assaulted the woman "on a daily basis" during a horrific campaign of domestic abuse.
He punched, kicked, stabbed, bit and choked terrified Antonia Gillespie and held her head under water as she was having a bath.
Hamilton Sheriff Court heard that on one occasion the thug shoved her face into dog faeces.
Walker, 27, admitted assaulting Antonia, 21, and directing an abusive course of conduct against her between May 2018 and July last year.
The attacks happened at addresses in Hamilton and Uddingston, and at the holiday home of Walker's parents in Portpatrick, Wigtownshire. He also admitted assault and abusive behaviour towards a previous girlfriend.
Sheriff Andrew McIntyre said: "The charges disclose a concerted and relentless campaign of abuse against two women. It involved repeated acts of serious violence, controlling behaviour and numerous offences that harmed, degraded and humiliated these women.
"It's abuse of the most serious kind to be prosecuted in the sheriff court. It's plain that you represent a serious danger to the public, particularly women with whom you form a relationship."
Walker will be supervised for two years on his release from prison and the sheriff imposed non-harassment orders, banning him from contacting the victims indefinitely.
Jennifer Cunningham, prosecuting, said Walker and Antonia had a "turbulent" 19 month relationship. Walker was jailed in 2019 for assaulting her, but they got back together when he left prison.
The fiscal added: "She describes being assaulted on a daily basis by the time he was jailed in 2019. On a number of occasions he held a knife at her throat and threatened to kill her."
Walker also admitted abusive behaviour towards a previous girlfriend in 2011 and 2012.
Defence agent Ian Scott added: "According to a psychologist, he is beset by cannabis use disorder and alcohol problems, and has a borderline personality. He comes from a loving family and it appears he developed issues independently.”