For the past 6 years:
Moshiri, for appointing all the wrong people and not fixing the problems. He threw money at the club and expect things to work out.
Walsh & Koeman - obviously, less said the better.
Brands
Doesn't not own up to his mistakes, I think he said the a fan that he didn't make the transfer decision. Doucure, Iwobi, Moise Kean, Ben Godfrey, Digne, Andre Gomes, Yerry Mina, Gbamin, Nkoulou etc. were all his signings. He may not have put his final signature on paper but might as well be him by leaving things late so that the manager given no choice to sign off on them.
And if by some miracle, he didn't make the transfer, then what the hell has he been doing in the club? It's not like our Youth academy is getting better.
Bill Kenwright
He is the chairman of the club. he should be running the club smoothly. But the medical, scouting, money allocation, branding, etc. have all regressed under his leadership. I'm not too sure what Bill Kenwright does after Moshiri took over.