Working through in some kind of order:
Ozymandias - was given Precise Blow; I saw this on another gamer's homebrew update (credit to Liam Callebout). Based on the source material, especially the Before Watchmen comics, this just seemed very fitting for a man who always plans every single move he makes, and who has the coordination to parry a bullet with a piece of furniture and later catch one in his hand.
Nite Owl - I chose something simple for Nite Owl, Master Fighter. Functionally this is worse than the rerolls Silk Spectre gets from Unarmed Combat Master, but I didn't want to duplicate what she had, and at a similar Reputation cost Damian Wayne has the same Trait. With Bonebreaker, Brutal and Arrest already I feel it is a fair trade-off and upgrade.
Rorschach - I felt Cruel fit his efficient way of putting foes down; while the character has some nobility about him, he is incredibly brutal and the rule functionally fit with his existing repertoire. On top of this I added a one-shot attack based on firing his grapple gun at a hapless target.
Silk Spectre II - I had a few thoughts about stuff that could fit, but a lot came down to 'gamey-ness', and so when I thought about Silk Spectre I recalled two sequences in the movie in particular (the street gang fight and the prison raid) when she just mows through hordes of mooks, and Devastating Blow seemed the nearest representation of that.
Let me know what you think, comments and critique welcome!