I"m not sure where to begin, there"s been so many. Off the top of my head:
Alexander Tonev: By far the worst player I've seen in a Villa shirt in recent years, and that"s saying something. I've never seen someone consistently kick the ball into Row Z so frequently, it was quite comical. He then got loaned to Celtic, got banned for racism, and was promptly released.
Bosko Balaban: £6 million pounds, played 8 games, never scored and was sold on a free.
Emile Heskey: Averaged a goal every 10 games, on 70k per week. He was absolutely abysmal. Like Tonev, it was almost comical at times.
Charles N'Zogbia: Probably the laziest player I've ever seen, with a stinking attitude as well. He cost 9.5 million about 5 years ago and he's probably played 3 good games. All he's done lately is argue with fans on Twitter while collecting his 65k per week wages. The frustrating thing is that he could actually be good if he wanted, but he just doesn't care.
Alex McLeish: The worst managerial appointment that could've possibly been made. He'd just got the club's biggest rivals relegated while playing absolutely dire football and he walked into the club as the top-priority target. Apparently Randy Lerner was shocked at the backlash when he was appointed. I still can't get my head around this one.