My crab out in a open
 

This is the first time he came out for a full view.I had him sense September, he came with the rock. Has one claw, most of the time, shaped like a spoon on a end.He is dark purple, with lighter bands on the legs. Never touched anything with the exception of moving smaller rocks and frags what are not placed to his likening.

The angle which he holds that claw makes me think he's been injured or something. Odd that he doesn't have two of those claws, also.

While I always try to keep any crab that I have, most people suggest that crabs with those flat tipped claws are harmless.

I know, he was holding it up in a air. A few months ago he had one claw as well, then it had growing back, he had two and now he is back having one.
I wonder if his other claw is not being used enough to develop. I don't have any fish what would go after him. But he always been very shy, hides with every movement from me.

No...that crab is involved some heated debate with some other critter in the tank. Could be another crab, shrimp or a fish.