No one knows for sure because we have dinosaur bones, not flesh but, the flank is its weakest spot. If you are a smaller dinosaur, say dilophosaurus, you will slash and tear at its flank. However, an allosaurus could charge it down and bite its exposed neck and underbelly. Or allosaurus could go for a head on assault.
Cheers.
he has a weak spot for red heads
After bathing in the River Styx his "Achilles Heel" or weak spot was his underarm.
terds
his weak spot
Achilles' heel was his weak spot thus the saying that someone's weakness is their "Achilles heel."
In the crust the weak spot we have is the Magma Chamber. But, deep down to the mantle such weak zone is the Asthenosphere.
Stomach
his pride
His heel
terds
The weak spot of an alligator is it's somach
An "Achilles heel" is a person with a weak spot.