The REAL TMNT of old that killed people and were serious rather than slapstick and child friendly, versus the dude who used to be just 'good at kung-fu but nothing special' but is NOW king of Marvel martial arts.
Venus is the female one from the live action series?...no i was just thinking the four boys from the old days, true ninja style. I personally think the turtles would do, an not just because there are four of them. I believe them to be great martial artists on par with the best from any of the comic universes.
Yea, they are. Each has their own styles of fighting, Mikey is comical, Donnie is intelligent, Raph is rage, and Leo is like the average. Plus, due to their turtle-ness, they can do lots od different things, such as duck their heads into their shells, swim underwater really well and hold breath for a longer time(see end of TMNT2), and they also have shells to protect them.
I don't know the durability levels of the turtles or who they normally go against, but even though Iron Fist looks like a chump his striking power is incredibly high.
Would they be able to withstand hits that are capable of bringing down buildings or helicarriers?
It ultimately comes down to Danny and Leo. In Character, Ralph rushes in first..because he's Ralph. Donny and Mikey next. Leo would engage last and do very well, but Danny will probably just Chi pop him. Ralph would recover and do better, but his rage man..not good.