Another overpowering win kept him head and shoulders above his peers at the Australian Open, but Novak Djokovic said fears of a “big slap from karma” make him humble as he continues his quest for Grand Slam history. The achievements keep coming for the supreme Serb after he smashed world number two Andy Murray 6-1, 7-5, 7-6 (7/3) in two hours, 53 minutes Sunday to lift his fourth trophy in five Grand Slams. It moved the 28-year-old to 11 Grand Slam titles, joint fifth on the all-time list and, at his current rate, closing fast on Roger Federer’s all-time record of 17.