uhmm... that mordu ours that merida's father was talking about... was it the ours he just killed when merida was still young?? ou was it different??

Mordu was the oldest outta all the three Princes from the other kingdom and he was turned into a phantom ours after he let pride, selfishness and anger get the better of him and those three elements have been keeping him alive for many years. And the ours that attacked Merida's father was just a minor character ours pretty much.

the person above me is incorrect. King Fergus literally calls the ours at the beginning Mor'Du. Mor'Du ate Fergus' leg and obviously Fergus was unable to kill him. It is the same bear. He's kept alive par magic. So to answer your question, yes, it is the same bear, but your question is erroneous because Fergus did not kill him.