worst motors of all time

Isuzu 4 banger that was used in a Chevy Luv truck, I had one of these and had the dubious honor of being the slowest car at a huge points meet at Ohio Valley Raceway back in the 80's. I ran triple Z class and they just gave me a trophy and ask me to leave because they didn't have time to waste letting me make a pass.
Any motor that the used in an Intrepid. There are so many nice Intreped bodies in junkyards because the motors were crap and they wouldn't last long enough for people to even crash them.
Just about every motor Mitsubishi made back in the 70's and 80's (and probably still today)
Renault motors
Fiat motors
I could probably list a few more.

The early Intrepids were fine...they used the minivan 3.3 and the OHC 3.5 V6's. 200K from either is normal. (My stepfather's first Concorde went to my brother at 210K, he sold it to another guy in his platoon with ~240K, the guy promptly drove if from North Carolina to Seattle.)

The later ones had either the very-problematic 2.7 or the much-better 3.2 engines.

The Mitsubishi 3.0 V6 was a good engine...seen many with over 300K in livery Caravans. It would need valve seals around 120-140K...though it would easily run another 100K with bad seals!