Vanilla Ice's "Extremely Live" which was his second album. Not that the first one was good, but the second one killed his career so bad, there was no recovery. One line was "...driving down the street with my windows down/ I'm on my bike, headed for the mic". He should have been slapped, and slapped hard for that.
MC Hammer's "The Funky Head Hunter", for the same reasons as above. It was his failed attempt to show his critics were wrong by saying he couldn't make a good album without the samples. He also tried to be a lil "gangsta". That was all Suge and Snoop's doing and their donation to an already bad idea.
This next one pains me to say, because I am a fan of his, and met him on a few occasions; one of the coolest dudes ever....DMC's (from RunDMC) solo album "Checks Thugs and Rock 'n Roll". It was horrifying!
Next, it would be, Cedric Ceballos' (former NBA player for The Phoenix Suns and the Los Angeles Lakers) rap album "Nuff Ced". To be fair, the other NBA players attempted this failed pretty bad too, but Cedric's was the worst of the worse.
Finally, the most criminal attempt at making a rap album would be The Surf MCs and their album "Surf Or Die". Cedric's was close, but AT LEAST Warren G did some production on his.