Aside from the tutorial boss, these were the only 2 bosses I beat so far in my 6 hours with the game. Mostly exploring , getting steamrolled by the occasional boss I encounter. Lion Claw worked great on these encounters. Its an ability that comes with this Claymore and has great stagger as well.
Leonine I may have beaten on my second attempt. It went down fast with my loadout. The Demi Human Chiefs went down after a few attempts after returning with the better sword and a few levels. I was dying on them for a while even with co op previously. Trying different things, powering up is huge in these games.