From a pure progression view I would say Hyperion. Eventhou Blade is still very good for act 5. But the most important question is. Who do you use most. And who do you enjoy playing the most. That should be your first rank 5.
I was only recently able to get Hyperion as a 5-Star but have been enjoying him. Having that consistent Power Gain has helped me to keep being able to launch specials consistently, even when my opponent is playing defensively or when I'm on a lane that makes it difficult to land basic combos consistently. He's also been consistently helpful for me against Buffed Up and Diss Track nodes, though that might not be a concern for everyone at the moment. Plus if your Alliance competes in AW, he can still be good defender, depending on what tier you're at.