The Music There was nothing mundane about the track chosen. It was a slightly faster tempo version of Locus and Felix theme. Sure, it wasn't as CRAZY as the Ice Fight in season 9 (still my favorite track in all of RvB), but you know what it was? Suitable.
It was pretty generic, and didn't match the energy of the scene, even if it was more grounded compared to previous sequences. I also don't see how you thought saying "IT'S A CHARACTER'S THEME BUT SPED UP SLIGHTLY" will somehow change my view, and make me think that the track in any way matched the scene.
Because the fight isn't meant to be >"SUPERHARDCOREACTIONPACKED". It's a buildup. Felix is toying with a couple of prison guards as Locus and the pirates slowly storm the ship. It's building tension, because you have no idea what these two characters are doing.
I don't think you know what build up means. The fight ITSELF is built up somewhat when Felix is chatting with the crew, and reveals his true intentions. This is when the tension is at its most high, because we know there's going to be a fight any second now, and the fate of the men in the bridge who were actually somewhat likable, are up in the air. And when the fight does happen, there's a release of tension with the quick burst of action. Locust and his grunts swarming the ship doesn't really add tension, since we have no attachment to the guards being mowed down, like we did the ones who were with Felix on the bridge. Not to mention how Felix straight up told us that he and his men were going to take the ship and the prisoners, so it's not like anyone was on the edge of their seat thinking "Oh man, what is Locust doing?!!"
First of all, he's not acting suspicious while they're hailing him. He's pretending that his pelican has broken down. They mentioned responding to a distress beacon coming from his ship. Which is why he pretends his coms aren't working (not to mention, it would ruin the reveal that it's Felix coming to stir up trouble).
Ship breaking down =/= communication difficulties. Especially when he makes it appear that HE is simply unable to respond to them, yet he can hear them. It's made even more dubious considering that if he managed to send a distress signal, that would mean his ship was capable of broadcasting said signal. So, if his ship CAN send signals and receive them, then that means he is actively refusing to identify himself. Like what, do you think he came up with a scenario where he was a Pelican pilot who stopped dead and sent out a distress signal because his mic didn't work? Instead of just going to where he was going in the first place?
You can easily rework the scene to include the reveal of Felix. Just skip to the part where the Captain tells the Pelican to dock and orders his men to greet the shuttle, and cut out the headlights and mention of said headlights from the crew.
He is a narcissistic sociopath. He's incredibly full of himself (Locus always complains about his ego, he has a HUGE tendency to monologue), he's cruel, he's manipulative. He has everything you need in a good villain.
You just gave the definition of "narcissistic" and "sociopath". Both of which are pretty much mandatory traits for the whole "Charming, Manipulative Villain" trope.
Correction: There are two kinds of scenes that are constructed this way. The one you describe, which is a reveal ("Oooooh shit, he's back! Hold onto your dicks!"), and the buildup. ("Oh man, that guy looks like a badass! I wonder what trouble he's going to cause!") This was the second one.
It's both. And that's why it falls flat on its face. Fans didn't recognize him at first, but deduced that he must have been the shark dude from like, Season 9. But since he was just some mook, the scene doesn't instill a sense of excitement, but of confusion. Because at first, you're busy thinking "who the hell is this guy?", and when you remember, you think "they brought HIM back? He was basically just a grunt with painted armor!" Hell, you might as well have made a brand new character. That way, it wouldn't muddy up the dramatic reveal with confusion as to why Shark Face was deemed important enough to return.
Because Felix and Locus were strong opponents for our heroes, but they needed help. Now they have the Councillor, and Sharkface, and a bunch of inmates.
Why do they need help? With their gang of invisible, alien weapon toting agents, they seemed pretty capable already.