Stefano Modena.

Managed to beat his Brabham team-mate Brundle.
Then destroyed Nakajima by at least the same margin as Piquet.
Marvellous drive in Canada and especially at Monaco in 1991.
Joined Jordan after team's promising debut season, but the second season turned out to be a disaster, which also destroyed Stefano's career. He was anonymous in races and got no notice from stronger teams from there on...

And I agree that Martini was also definetely better than his results show. On several occasions he qualified his Minardi into Top3!