Sometimes, I get the feeling there is something inside Jagmohan, aside from the perpetual anger and thirst for revenge. I don't think Thakur has it, by the way.
I could see him having a soft spot--fear of having things taken from him, loss, etc., like his dad and his wife. I think in some ways this explains his obsession with getting Abha away from Karan, aside from the Thakur angle.
I believe Karan's dadi said something to the effect of Abha being a light, like his mom. Karan's mom was gentle, kind, and had presence. And Abha and her actions now or later are going to remind Jagmohan of his wife, his loss. I don't think Jagmohan was always angry...he became this way with the passing years. I'd love to understand more about him and his relationship with his wife, given their "opposite" personalities.
I fully believe Jagmohan will accept Abha before Thakur accepts Karan. It's not going to be overnight but I think something Abha does will bring it all back to his wife. I've been wondering about this since Dadi showed Karan her wedding picture but noone in the house talks about her except Karan and Dadi.