Sally's not going anywhere in life due to her drug problems, has no children and doesn't speak to her family anyway.
Sukhdev has two young children and is a hard working business man. Looks like some dodgy fraudulent behaviour is involved there, but what business isn't that true of? He's clearly a hard worker as he spends so much of his time away from home. His wife has been diagnosed with depression and his death could tip her over the damage and be hugely detrimental to their children. I don't get the relevance of not supporting Lucy, just because he had sex with her doesn't mean he has any obligations to find her a ****ing house several months later.
Whilst I empathise with John's childhood troubles, that's not an excuse for him to assault his pregnant gf. He's an utter **** that is contributing nothing to society but violence and misery. Although his gf is pregnant, even if the baby survives his assault it is extremely unlikely that he would have anything positive to contribute to his/her life anyway.
Therefore, I would save Sukhdev.