What Is The Best Example Of An Automotive Achilles' Heel?

Most super heroes have one weakness or Achilles' heel which if discovered can bring them to their knees. Some cars have a similar weakness common to their model or even manufacturer. What is the best example of an automotive Achilles' heel?

If you've spent any time reading Greek mythology or comic books you are likely familiar with the concept of an Achilles' heel. Without delving into a QOTW mythology lesson, Achilles was a Greek hero who was dipped into the magical river STYX by his mother as a child. The water of the river washed over Achilles granting him the power of invincibility except for the small area of his heel where he was held by his mother. Ultimately, this one area of weakness led to his demise when an arrow landed in Achilles' heel during battle and killed him.

While magic rivers later used as crappy band names and Greek battles might not have a lot to do with cars, the story of Achilles' does, at least in the context of this week's Question of the Weekend. We want to know, what is the best known automotive "Achilles' heel"? What failed car might have been a success if it weren't for that one design flaw? What successful car is known for its common and inevitable point of failure years later? What did the manufacturers overlook, under test, or generally screw up while they were designing a vehicle that was otherwise well loved or at least initially well sold?

I have to stick to what I know in answering this one and point out the International Scout's notorious rust problems. While many old vehicles, especially in the North East, are prone to rust, the International Scout took a "rust prone nature" to an entirely new level. Even in the driest and most rust free areas of the country, finding a rust free Scout is nearly impossible. Scouts are best known for their bullet proof nature, until they get too rusty to drive. In many cases, this didn't take long.

I've pointed out the otherwise bulletproof IH Scout's less than rust proof nature, so tell me, what do you think is the best example of an automotive Achilles' heel?