There are very few players in baseball history who spent the majority of their careers as a designated hitter - only 19 men had 1,000 plate appearances in their career while starting half their games at DH. Of those, the worst was probably Glenn Adams. Adams batted .338 in 1977 for the Twins, and then spent the next four years living off that season while being a slow, below-average hitter with no power and mediocre average and on-base abilities. Adam Dunn has at least showed power and on-base ability during his DH years - Adams showed nothing except a fluke season and the ability to be a decent pinch hitter.

The single worst season by a DH is probably Ted Simmons in 1984 - he batted .221, had no power, didn't get on base, no speed, and he played a full season.

Adam Dunn IS the worst DH in MLB baseball history.

Adam Dunn gets my vote. In 317 games as a DH, Dunn is hitting .202 with a .321 OBP and .412 slugging percentage. He strikes out once every 2.5 at bats and his K:BB ratio is 2.5:1.

Considering the only job the DH has is to hit, Dunn has failed dismally.

The Yankees once (in 1988) used Rick Rhoden as the DH. Now, Rhoden wasn't a bad hitter as pitchers go (he drove in a run with a sac fly that day), but yes -- his standard job was pitcher.

The Yanx used a pitcher as the designated hitter.

This says a lot more about the 1988 Yankees than it does about Rhoden.