Alexander Povetkin was dangerous at times Saturday night, but Anthony Joshua ultimately did what he has done to all but one professional opponent. The hard-hitting British superstar dropped Povetkin twice in the seventh round and stopped him in the main event of a seven-bout card that drew an enormous crowd in excess of 80,000 to Wembley Stadium in London. Referee Steve Gray stopped their scheduled 12-round fight at 1:59 of the seventh round, as soon as Povetkin hit the canvas a second time. The 28-year-old Joshua went off as a 10-1 favorite, according to most Internet sports books, and eventually overpowered Povetkin accordingly. The 6-feet-6, 246¼-pound Joshua (22-0, 21 KOs) retained the IBF, IBO, WBA and WBO titles and satisfied the WBA’s mandatory defense by beating Povetkin. He also became the first fighter to knock out Russia’s Povetkin, a former WBA heavyweight champion. “Alexander Povetkin is a very tough challenger,” Joshua told Sky Sports during his post-fig...