I'm debating between Jeff Skinner and Noah Hanifin. Skinner overall is one of the best natural goal-scorers in team history but played no defense and if he wasn't having a good season, he was useless.
Hanifin looking back on it was overhyped. He wasn't drafted into the best situation but at the same time, Pesce and Slavin both turned into what Hanifin was drafted to be, someone who was reliable. Traded for Dougie Hamilton who played the same number of seasons and became way more of a fan favorite than Hanifin.
I'd probably pick Skinner, he had 63 points his rookie year and was looking like a potential 100 point player. He unfortunately peaked for Carolina after turning 19.