Andoni Goikoetxea was named by The Times as the "hardest" player of all time. Here's the tackle which put Maradona out of the game for some considerable time. Goiko (apparently) still keeps the boot with which he made the "tackle".
For us culers, this foul marked the moment of Maradona's decline - it was during his time off the pitch that he began to get into cocaine and although it didn't get serious until after he signed for Naples, his drug problem had begun.