Some other guys I will add:
Pavel Zacha - former 6th overall pick who was expected to take a step forward. Unfortunately he seems to be doing the opposite
Ryan Spooner - after a solid year with a career best point per game and goals, there was hope that Spooner would finally become a reliable scoring threat with the Rangers. With 5 points in 36 games and a early-season trade to Edmonton that hasnt changed much, Spooner will need a bounceback season and a half if he wants to get another NHL job after his current contract
Charles Hudon - after a promising rookie year where he scored 30 pts in 72 games, Hudon has struggled to score with only 4 pts in 23 games and has found himself as a frequent healthy scratch
Riley Nash - after a 41pt breakout season with Boston, Nash signed a UFA deal with Columbus. Unfortuantely for CLB and Nash, it seems like the 41 pt season was a blip and that Nash is closer to the 20 pt player he was beforehand. Even so, his 4 pts in 40 games is a disappointment and CLB needs more from him
Robbie Fabbri - Fabbri put up 37pts in 72 games as a 19/20 year old and was well on his way to matching those totals the next year, but he suffered suffered a serious knee injury. He reinjured it and ended up missing the final 30 games of 16-17 and all of 17-18. This year he has struggled with other injuries and has only 4pts in 18 games so far
Jesse Puljuarvi - With only 6pts in 31 games, its safe to say that most people expected more from Puljuarvi
Carl Hagelin - 1 goal and 5 pts in 22 games is not enough for a player with Hagelins tools. This is the one of the worst offensive stretches of Hagelins career.
Val Nichushkin - when you leave your team in a contract holdout and then come back on a relatively expensive extension, you are expected to produce. With 0 goals and 7pts in 33 games, Nichushkin has been a huge disappointment so far
Andre Burakovsky - every time I watch him, I'm impressed and amazed. Impressed by his speed and skill, and amazed that he only had 9pts in 37 games. He looks like a 50+ pt guy out there but he produces like Chris Tanev.
Tyler Toffoli - 16pts in 43 games is not enough from a player like Tofolli. He is on pace for his worst season as an NHLer and while LA has struggled a lot, the struggles would be a bit less significant if he was able to step it up
Kevin Shattenkirk - 10pts in 33 games is not enough from an offensive DMan who is earning $8mil this year. He is only playing 18mins a game, too. NYR needs him to do more
M.E Vlasic - after posting a career high in goals with 11, Vlasic only has 1 after 42 games. He is a -13, which would be a career worst and the first time since his 2nd season that he posts a negative goal differential. The biggest issue is that he isn't even defending as well as he has in the past.
There are tons of other guys I could add but these are guys that came to mind
Ivan Provorov, Brady Skjei, Derek Brassard, Derek Ryan, Oliver Bjorkstrand, Pavel Buchnevich, Christian Fischer, Anthony Mantha, Mikhail Sergachev, Mats Zuccarello, Will Butcher, Sam Bennet, Wayne Simmonds, Kyle Okposo, Duncan Keith & Jeff Carter are all up there too