2 and 3 The difference being 2 is praising the attribute itself, whereas 3 is praising him.

You would often say ‘I admire his bravery’ to suggest that you DON’T know or like him more generally.

2 and 3

The first one is not natural because it implies there are other versions of that are not brave. . . "I don't like him when he is cowardly, but I like him brave." It's not the sort of sentence one needs very often. As Cayle said, 2 and 3 are fine, but mean slightly different things.

2 or 3. Maybe better to use 'admire' instead of 'like'.