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

Mordu was the oldest outta all the three Princes from the other kingdom and he was turned into a phantom orso 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 orso that attacked Merida's father was just a minor character orso pretty much.

the person above me is incorrect. King Fergus literally calls the orso 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 da magic. So to answer your question, yes, it is the same bear, but your domanda is erroneous because Fergus did not kill him.