Have you seen the Alechi Raptors near Moore Crater? According to the notes, Alechi's fierce soul lives on in the Alechi Raptors.
But it can only truly manifest itself in one raptor; you'll have to search through all the creatures to find the especially fierce one that contains Alechi's soul.
We're counting on you.
Watch out; I'm concerned that a raptor imbued with vicious Alechi's soul will be particularly - feisty, shall we say? And by 'feisty,' I mean 'deadly.' But doesn't 'fesity' sound so much nicer?