Austin Adams is the most unhittable no-name veteran pitcher in baseball. He's only stayed healthy enough to throw 109.1 innings across parts of 7 seasons in the bigs, but has racked up a baffling 166 Ks and allowed just 64 hits (.170 career BAA). This season, he landed with the DBacks on a minor league deal, and in his first 12.1 innings since being called up, he's somehow managed to collect 7 holds on the back of 18 strikeouts.
Is there another pitcher who doesn't have anything close to elite status, who has mowed down MLB batters at the same rate for their entire career? He walks too many, which probably puts him into the effectively wild rather than dominant category, but I still found his numbers to look like quite an outlier.
Edit - Ok I went and figured it out, here are the top 10 all time career K/9 for pitchers who have at least 100 MLB innings:
Josh Hader 15.09
Edwin Diaz 14.81
Aroldis Chapman 14.75
Dellin Betances 14.45
Felix Bautista 14.38
Craig Kimbrel 14.33
Devin Williams 14.07
James Karinchak 13.94
Spencer Strider 13.88
Austin Adams 13.66
Dude is 10th all time in career K/9 and couldn't land a major league deal this past off season....