Which dogs have the worst bite?

Naturally, "worst" is a product of both bite pressure and tooth sharpness/arrangement, but here are the top four hardest biters among domestic dogs:

Mastiff: 556 Pounds per Square Inch
Rottweiler: 328 PSI
German Shepherd: 238 PSI
American Pitbull: 235

     In the wild, Spotted/Striped Hyenas (which eat bones) can clampw at 1100 PSI,
     Saltwater crocodiles, at 7700 PSI, have the most powerful jaws of any living creature (including tigers, rhinos, grizzlies and sharks) but their jaw opening muscles are quite weak, which is why the crazed humans who wrestle them try to lock down their jaws — not hard to do, if you can ride out the thrashing.
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Source: http://forums.sherdog.com/threads/the-top-20-worlds-strongest-animal-bite-forces-measured-in-psi-new.2393047/