From my limited experience with lunare wrasses, I've had one kill green chromis and harrass a blue devil. It gets along well with a yellow tang and a regal tang which are similar in size. I wouldn't put one in a tank with small timid fish. It also will do quick work of snails and has tried to eat a couple of large hermits. My wrasse is going to be fished out of the 120 gal FOWLR I maintain on Monday so I can add more community type fish.
I just traded in a show quality lunar wrasse of about 5" the other day. He was way to aggressive and was blocking me from putting any other fish smaller than him in the 90 gallon tank. At one point I tried putting a Fiji Blue Devil Damsel in there and he ate it within an hour or so. That's the point where I decided I would have to trade him in
.
I have a post on here about trying to put another fish in with him, you can read that post and find out about other people's horror stories.
IMO If you don't have a large tank and introduce him last, you shouldn't really bother!