OLDWICK, N.J.--(BUSINESS WIRE)--A.M. Best has affirmed the financial strength rating (FSR) of A+ (Superior) and the issuer credit ratings (ICR) of “aa-” of Sun Life Assurance Company of Canada (Sun Life) (Ontario, Canada) and Sun Life and Health Insurance Company (U.S.) (SLHIC) (Windsor, CT) – the core insurance subsidiaries of Sun Life Financial Inc. (SLF) (Ontario, Canada) [NYSE:SLF]. Concurrently, A.M. Best has affirmed the ICR of “a-” and existing debt ratings of SLF. Additionally, A.M. Bes