The easy answer is DT, which was pretty much terrible forever for Minnesota before we drafted Nathaniel Hollis.
Another good answer would be corner, which is historically the worst position group for the Vikings, and it isn't that close. Statistically the best corner ever for the Vikings is probably Devon Drummond, which tells you what you need to know. Drafting McKinney and following that up with Isaiah Jenkins has seemed to pay dividends, although both are very young. McKinney looks poised to be a perennial pro bowler going forward while IJJ the jury is still out on but as a CB2 I think he will be good.