One way we can assess a player's contributions to his team is Box Plus/Minus, a metric that estimates the number of points per 100 possessions a player contributes above (or below) average using stats found in the box score. BPM has never seen a college player like Williamson. Among players who qualified for the points per game leaderboard at Sports-Reference.com and appeared in at least 10 games since 2010, the first year for which data for all players is available, Williamson's mark of +20.4 ranks first among 25,793 individual seasons.
Another way to evaluate a player's contributions is using player efficiency rating. Williamson's PER of 41.9 is the best mark by any player who saw action in at least 10 games since 2009, the earliest year for the data.
I look forward to seeing how ACC teams defend him.