There have been so, so many over the years. It's far easier to list the players who have arrived with a reputation and lived up to it.
Some of the much vaunted players who did play well on the field turned out to be boatloads of trouble off it as well.
Since Juninho, I can hardly think of anyone who was bought for significant money and significant reputation who lived up to their reputation on the field, and left without damaging the club or badmouthing it or leaving under some other cloud.
For example - Alves - never looked anything like the player we thought we were getting.
Ravanelli - looked great on the field but created huge issues in the dressing room and within the club.
Merson - great on the field but left when Villa sniffed about and blamed the club for his own demons.
Ziege - looked great, turned it on and then left as soon as the opportunity arose.