what are the triphop artist that really suck?

I am new in this genre of music; most people i know dont even know what this genre is. Like most people, i came into this genre through Portishead, and massive attack. Most of what I am seeing on this site is positive backup on the bands. I would like to know what are the bands that arent that great, according to people who have been into this kind of music for awhile so i can stay away from them. Or listen to try and figure out why they suck, then base my later judgements on a better tuned music taste. I would appreciate it.