Complex sentence: Cummiskey looked at Denis Curley as a little brother, and Cummiskey wasnted to murder Dugan himself, so, Coonan seeing the opportunity for a new violent recruit, and gaining one of Spillane's top enforcers, offered Dugan up as a peace offer.
Split into simpler sentences: Cummiskey looked at Denis Curley as a little brother, and Cummiskey wanted to murder Dugan himself. Coonan, seeing the opportunity for a new violent recruit and gaining one of Spillane's top enforcers, offered Dugan up as a peace offer.