Nothing has tried to go after my emu, however we do have an unknown animal who kills his chicken and duck friends if they are not properly secured. We've never seen it, only the remains of the chickens it has killed.
Emu's too big for most predators [although apparently sometimes if they sleep outside they can be killed in their sleep by sneaky beasts like foxes and weasels] and his species is known for stomping predators/any animal they don't think belongs in their space to death. My emu, however, is too friendly and has been seen to willingly allow a possum to share his shed [he did try to peck the possum while I was removing it, though. Mean little bugger, I had to carry him out in a bucket so he wouldn't bite me -the possum that is.] until I saw it and got it out of there. Maybe he thought it was a weird new cat; he seems to know that the cats are friends and only chases them for fun, not to harm them.