Sharks have a lot of street cred for all their seal and surfer eating, but I believe the swordfish to be the biggest badass of the seas. The shark is a thug, while the swordfish has style. The shark is Chris Penn as Nice Guy Eddie, while if fish had wallets, the swordfish's would say 'Bad Mother Fucker' on it. And if any more proof is needed, then I'd submit that the swordfish is faster than the mako shark. Moreover, in the event a mako can catch a swordfish, then the smaller swordfish can kill the mako with, what else but its sword!
The swordfish fits into this section on exceptions to nature's rules because it's warm blooded. It can heat up its eyes and brain and go into a fish turbo mode. Note: it heats its brain, rather than its fins or sword, because the brain is the greatest weapon of the underwater badass.