" Toh teri shikayat Kya hai, ki usne rishta nahi nibhaya, ya jaan nahi di? "

This dialogue hits hard. Dev never blamed Sona for leaving his family, his only complaint was that she left 'him'. He knew that Ishwari never wanted Sonakshi, and always blamed her.

#KRPKAB

His family, did not deserve Sonakshi. He not only questioned Ishwari's expectations from her, he tried to make a point that the main reason was not "rishta nibhana" that Ishwari was talking about
#KRPKAB

He knew by this time that Ishwari did not want Sonakshi in his life, all the reasons and complaints were hollow, meaningless. This was something more than a taunt. It was an attempt to make Ishwari realize what she's been doing subconsciously. But she never understood.
#KRPKAB