[[[[ STORY SPOILERS ]]]
Regarding the Character, "The Harbinger"
A — The name “Harbinger” is cliche, already used by Mass Effect and MANY other Sci Fi books and media, and seems like a low-effort name, especially compared to some of the well crafted, unique and top tier names from the books which sound mysterious or interesting
B — Having the character introduced midway through the game and then defeated ( A FEW hours later in real time ) by the end without even knowing their full intentions ( besides being allied with the Brutes out of convenience ) feels cheap and nonsensical, and given the likelyhood that the Harbinger and/or endless are supposed to be a top tier threat, even by the forerunners, makes that not seem believable, given that the in-game presence of her character and support units didn’t feel formidable etc OR at least explained WHY the Harbinger and Endless are deemed such a threat
C — The visual design and armor of the Harbinger was too safe and standard looking, and felt too similar too the Khan Makyr from Doom, yet even less distinct and less unique and not terrifying like Destiny’s witch Queen which has a presence and show of power by controlling an entire region and army
D —The floating Octopus Monkeys look awesome but feel like pushovers in-game, a lot of the time just floating in place, which makes it even less believable that they overtook a MONITOR of a Halo ring who has legions of Sentinels at their disposal and their own powerful energy beam defense.
E — Other concepts of the Harbinger ( even other variations from the same artist that made her final look ) looked more interesting and memorable and “less safe” and more exciting than the final design choice
F — Having only those flying minions with lightning rifles made the Harbinger feel like a weak character/faction compared to other villains in the game who had legions of forces and I know it’s because the rest of the Endless aren’t unleashed yet, but they should have been, so at least it would have made the player feel like the Harbinger was an actual threat by experiencing the effects of encountering her Endless forces or the effects of her successfully starting to repair the ring and the consequences of that process beginning and effecting the map or stability of the island and environment
— SHOW us That the Harbinger is powerful and formidable, not just an “i wiLl uNleAsh tHe eNdleSs diAtRibE” cliche Villain speech followed by a boss battle and no payoff of encountering the Endless except as a tease for future DLC OR you could add tension by have her starting to successfully repair the Ring to create the suspense that she COULD succeed at gaining control of Halo and giving the Banished an operational superweapon instead of her already being defeated in half a game.
G— Teasing the Endless as her species of big bads even more dangerous than the flood fell flat by not having them unleashed in the game. It ruined the plot twist. Imagine if the flood was only teased or talked about in Combat Evolved instead of having the player fight for their lives against the new parasite threat
H---- Why would I think the Endless are dangerous if the Harbinger, even with help from the Banished, gets defeated easily by Chief and a Rookie AI within a few hours ???
I ---- Having Harbinger and her minions destroy the monitor of the installation right as chief arrived felt contrived and silly. A BETTER idea would have been for the monitor to be helping chief and guiding Master-chief through the facilities against the Banished before they are ambushed by the Harbinger and a huge contingent of her forces who followed them to try and lure them into a trap/ambush etc…
J — Having the Harbinger unleashed and grab control of systems, RIGHT as Chief just happens to be found by the pilot after MONTHS in space isn’t believable or plausible timing, it seems like a plot hole due to the unlikelyhood of Chief arriving just in time to save the day, —> unless they have some viable explanation for such luck that I happened to have missed in the story that makes the timing plausible
Conclusion:
It would have been more interesting to let the Harbinger get control of the spires, start repairing the ring, the Terrain starts to crumble and change as it is transformed, have Chief “lose” in battle against her but he lives and escapes in a Razorback or Warthog run as her terraforming starts to mess up the landscape and crumble it, and then have the ending with Chief linking up with Arbiter or other Spartans elsewhere to regroup and formulate a plan to stop the Harbinger before the spires complete the Ring repair as the Cliffhangar/Finale
The problem isn’t that Halo had the Harbinger as a character, just how the character was presented and handled. The Didact, 343 Guilty Spark and the flood felt like real threats because they either partially succeeded, had immense power in the game or did damage etc, wheras the Harbinger felt Nerfed compared to having had more potential in the game or displaying an ability to succeed and was defeated too quickly etc