Hans looks really happy to see Anna alive here, like not furious, upset, bitter, outraged or even scared. When villains loose, they are always upset or angry to find out the heroes are okay, in fact Hans should be upset to see Anna and Elsa okay, if he wanted the throne so bad.
Expect he looks shocked and well, happy.
Don’t understand it, at all.
He does not seem happy but maybe I watched a different version of Frozen than you did.