Yeah he's always the first that comes to mind for me.
I suppose Graeme Hick in 1996 is another. Had averaged a tick under 50 for the previous 3 years, then suddenly averages 6 or something in the first part of the summer and that's it - never again is he a good Test player, despite plenty of opportunities.
Brian Lara never went anywhere near zero, at least not as a batsman, but he too fell pretty spectacularly from the potential second-best after Bradman in 1995/96 (had averaged 60 or so for his first 4 years) to no more than a decent Test batsman in 1996/97, and it wasn't until 2001/02 (when pitches flattened-out...) that he recovered his previous form, and only ever showed very brief glimpses of it in the intervening 4 years (1999 being the most obvious example).
Graham Gooch (to be a little harsh perhaps) averaged 61 in 35 games between 1990 and 1994, then just 21 in his last 10 matches (19 innings) with just 1 half-century. More players than not have a few bad games at the end of their career, and Gooch was 41 by this time, so normally that wouldn't be remotely surprising, but the fact that he'd performed so stupendously between 36 and 40 meant that it almost seemed he could just go on and on.
Cronje isn't really what I'd count as his fall had nothing to do with actual play and everything to do with match-fixing. What's more it was gradual over a time, and the hero-to-zero only happened when people found-out rather than when it actually happened. Greig too again wasn't to do with on-field misdemenours but betraying the team off-field.
I'm sure there are plenty more though.