I'll give you Grezda and Sadiq, neither kicked a ball. Suppose Hastie could be thrown in there too but he was a very low risk domestic signing who, so far, hasn't cut it. The rest contributed in some shape or form in their respective seasons so not having they were all shockers/poor.
Lafferty, Ojo and Ejaria all scored crucial European goals that literally earned the clubs millions more than their fees cost. Jones superb injury time cross for Alfie took us into the group stages and earnt us multiple millions alone. Worral was up and down performance wise but stood tall in a few old firms. Edmundson is still young and has looked decent each time we've seen him, which admittedly has been sparingly. Think the covid thing, rather than his ability, is influencing his inclusion in your list. Flanagan was essentially cover for both full backs and fulfilled that role, sometimes very well, sometimes not so.
Barker scored some crucial goals too, did flatter to deceive, but for free was hardly a disaster. King was loaned as a back up midfielder to a midfield that, that season, were barely injured. Stewart is praised constantly by Gerrard for his attitude etc and how he boosts training standards within the squad, he gets a pass from me. Coulibaly started like a house on fire, scored a few key goals and really looked the part, then got wiped out on the touchline by a St Mirren thug with about 4 mins to go in a game we were cruising. That set him back, then his dad died and he unfortunately wasn't the same player for us after that, it happens.
In short, Grezda was the worst signing as he was permanent and for the first team, cost a few million and contributed zero, yet even then we got some of that back selling him on so not the complete disaster some make out. Sadiq was 3rd or 4th choice striker, the semi showed why he was a poor choice but his career before and especially since, shows there is definitely something there that led to us taking a risk on him and he was just a loan.
Just got to take a look across the city to see that our 'failures' in the market are far less abject, expensive or as numerous as theirs and that is one of the key reasons we are champions and they are not. Not every signing works out, the trick is limiting those that don't. I've been more than happy with our recruitment tbh. Couple of failures, couple of average signings and a wealth of quality players.