Complex sentence: However, the Doctor had altered the Hand's programming so that instead of enhancing Skaro's sun, the Hand turned it supernova, obliterating Skaro and, presumably, the Daleks themselves.
Split into simpler sentences: However, the Doctor had altered the Hand's programming so that instead of enhancing Skaro's sun, the Hand blew it up. The resulting supernova wiped out Skaro and, presumably, the Daleks themselves.