This week our Dynamic Duo find out why Robin left the nest, er, Batcatve in Old Wounds

Dick Grayson reveals to his successor the secret of the strained relationships with his mentor and Barbara Gordon.Why you want to leave me? From My Big Fat Greek Wedding.

https://www.youtube.com/watch?v=s2nkin2qzUA

The Batman book I was thinking about was in fact Arkham Asylum: Living Hell written by Dan Slott, and the villain from that book was Great White Shark as Braydon had said.

https://dc.fandom.com/wiki/Arkham_Asylum:_Living_Hell_Vol_1