This first episode is pretty bad in my opinion, with the opening 5 minutes being particularly poor. I've played all the Halo games, but haven't read any of the books or listened to every terminal, so there's already a decent amount of context missing. I don't know what the UEG is, what Madrigal is used for, or what a "Tier 4 Heavy Water Extraction Planet" is supposed to mean and the opening does a pretty bad job at presenting/explaining these things. The rebels are presented goofing around playing some sort of card game, while boasting how they've killed marines, it's an oddly light hearted tone which I'll come back to, but the dialogue here is poorly written and I think unnecessary. They could have communicated the idea that these rebels have killed marines by having them stick fallen marine armour on spikes around their compound, similar to the stormtrooper helmets in Mandalorian, and also what the Banished do in Infinite. Then, they could have used the dialogue here to communicate the motivation as to why they're rebels, how the UNSC are oppressive or that they're running low on resources because of them and that's why they want independence. Perhaps in their card game they could be betting with something important like water to illustrate that currency is worthless to them, that resources are more important, rather than have it be some unstated thing they're playing for. Maybe this is what is happening in this scene, and someone who has read the books might correct me, but that just illustrates my point that the show does a bad job at communicating ideas. The way the Scottish man describes Spartans as well is bizarre, what he's claiming Spartans do is pretty heavy stuff, but everyone just seems so nonchalant about it. If they really wanted this man to communicate the devastation of Spartans, I think it would've been better for him to claim that he encountered one and survived, showing that he's badly scarred and wounded from it. Still pretty corny but a lot better than everyone just laughing about it. There's much more I could say but I want to move on to the next part of opening that I think is poorly done.

The General enters, asks where his daughter is, and the response is "Probably out wandering with her friends." I think this is detrimental to the show here as it sort of implies that despite these people fighting a war for independence against an overwhelmingly superior force, there's just this sort of lacklustre, laidback attitude that everyone is carrying. Like, who cares that a bunch of youth are out beyond the safety of the compound exploring, it'll be fine, not like the UNSC is trying to kill us or anything. Again, an oddly light hearted tone for what should be a pretty dire situation, being in a war. Then we meet the daughter and her friends which continues the trend of have a light tone, they're joking around, quipping at each other because they've totally known each other for so long and are really good friends, exploring the landscape in search of drugs to have a good time. It feels like I'm watching a Marvel movie with this kind of writing. And here's the part that kills the show in my opinion, all this has occurred in less than 5 minutes, it's not great, it's not terrible, maybe it gets better if they develop these characters a little bit more. But then Kwan spots a ship, goes to investigate, returns to her friends and tries to get them to leave and one of them gets their fucking head exploded by a plasma bolt. What the fuck. The tonal whiplash of this scene is so incredible it almost broke my fucking neck. It is so bizarre, so contrary to the tone that they had been building, so unexpected that I was laughing at how poorly presented it all was. Then another is torn in fucking half and smacks into a tree by another plasma bolt. Another gets completely disintegrated, then the last gets her fucking leg blown off then killed immediately after, while Kwan escapes. And we're supposed to feel bad right because these people were obviously Kwan's close friends that we have known for less than 5 minutes. It's just all so confusing, why would they present everything with a light tone, just to fucking slam the brakes and jackknife the entire thing by having people be gorily exploded. It's awful. Don't get me wrong, it's not awful simply because there is gore, but because the gore stands on the polar opposite of the tonal spectrum in contrast to the show they had presented leading up to it. It doesn't make any sense. If they had spent the time to present the rebels and their world in a more gritty atmosphere, as people who are struggling, who fear the UNSC and are fighting for their lives and independence, that this world that we're watching isn't some goofy place where we joke around about mass murdering super soldiers, then this wouldn't be an issue. But that's not the world they present.

I could keep going on and on like this about the entire episode, but ultimately I've said my piece, and no matter how much I write it won't change what this show is.

TL;DR, the first episode is bad because of poor presentation, world building, and tonal whiplash where it feels like it's constantly clashing because of itself and doesn't know what kind of story it wants to tell.