McIlrath. Literally drafted the guy for his fighting skills and physicality in the early-mid first round and went wildly off board to do so with . Um, yeah, you can find those things in an undrafted player.
Available at time of pick just from first 2 rounds: Cam Fowler, Jaden Schwartz, Tarasenko, Nick Bjugstad, Evgeny Kuznetsov, Charlie Coyle, Brock Nelson, Justin Faulk, Jon Merrill, Tyler Toffoli, Jason Zucker. Instead they drafted the least productive player out of the entire first round that wasn't a goale, Brandon Gormley, or Joey Hishon (and Hishon probably would've done better if not for injuries).
Dylan McIlrath is the obvious #1.
Lias Andersson is my #2. Rangers wanted Elias Pettersson and after he was taken off the board it was like the scouting team went, "well this kid's name is pretty close."
Reminds me of when the Oilers traded Taylor Hall to the Devils for Adam Larsson and everyone thought the Oilers thought they were getting Oliver Ekman-Larsson.