I'm judging this off hours spent trying to down. As well as a couple of other factors. Second place has to be my first oryx clear but that is Mainly due to seriously rubbish lfg groups. Think I spent maybe 12 hours first weekend on it. First place was skolas with increased enemy melee damage. I think that was 18 hours plus for my first skolas kill. Other contender was omnigul arc burn nightfall. After several returns to orbit that shit got rough. Honourable mentions go to Crota and vog and the warsat on fallen sabre before they sorted it