Of course every Winchester reunion is moving, but this one just has so many emotions attached. Dean’s just sacrificed one of the best friends he’s had in a long time to help Sam get back to him. Dean is anxious and worried. Hoping with all hope that it’s worked out, that Benny has found Sam, and it wasn’t all in vain.
And then he sees him and he’s washed over with relief because every time Sam leaves him he worries if he’ll ever see him again. He puts all his feeling into the hug that express all the words he’s incapable of saying out loud. And there’s a pang of sadness from the loss of his friend, but having Sam in his arms again makes it feel worth it.