First boarded by Insurrectionists, then Promethean/Covenant forces twice, and then by the Banished at the beginning of Halo: Infinite.
I get that for a ship its size it would be a highly attractive target, but surely after the twice successful boarding by the Prometheans/Covenant, they would have stepped up their anti-boarding measures. It’s almost as if they said, “Okay, it has happened three times in the past, but nobody will try it again.”
The Infinity is a space-faring city, and cities are notoriously impossible to keep 100% secure. Combine that with it being the single biggest non-Forerunner target in the galaxy… it’s going to get attacked.
Between the extensive civilian and military personnel, the Insurectionists understandably infiltrated.
The Prometheans teleported in, through no fault of the Infinity’s defenses.
Halo Infinite spoiler:
The Banished have combined Forerunner, Human, and Covenant Technology, and they’re one of the t powerful factions currently at play in the galaxy at the beginning of Halo Infinite, so them boarding is legitimately a case of the Infinity getting bested. Even Master Chief lost his fight in that first cutscene.
SPOILERS FOR INFINITE BELOW:
Well in Infinite, the Banished did use 4 large unknown breaching craft, which breached the hull of the Infinity. Now with that in mind, it would be rather difficult for the Infinity to kind of counter that. It was also unexpected too
Its the worf effect. Its the big thing so to show how threatening things are it has to get beat in a bunch.
Oddly enough Spirit of Fire has the opposite trope where because its the underdog it just gets to compete with ships larger and more powerful than it and come out fine.
Tbh, as much as I like the SoF, it really shouldn’t have survived what it did. Like getting rammed and cut in parts by a Covie ship as it was entering the Etran Harborage shield installation. We also going to ignore how it survived an assault from the Enduring Conviction for as long as it did until Jerome and Isabel took it down
Probably because it could have one shotted any of those Banished ships if they had attacked it head on at range. I mean it punched a hole through the Mantles Approach, there’s no way those cruiser ram ships would survive that.
Plus, Atriox may have used that slip space crystal to get his fleet so close to the Infinity to immediately start ramming actions from the sides.
I know people make a deal of complaining the Banished are put across as really powerful. But they’re not. They’re just opportunistic cowards and can’t win a fair fight. They take the Ark because they get the drop on the UNSC after Halo 5, they only stop the Flood because they turn the Sentinels back on, they probably would have been killed by the Guardians without the Weapon locking Cortana down, they only got the Infinity because they weren’t expecting a Banished Fleet to ambush them when they’re trying to free the Galaxy and Atriox; if Chief had extra set of eyes like he does normally that Brute would not be walking.
One man’s ‘opportunistic coward’ is another’s ‘smart strategist’.
The banished properly use their tech while the covenant was all caught up being prim and proper genociders.
Yes, but people frame it as them being powerful in the absolute sense of the word when they make that criticism of their portrayal. As if the Banished could have conquered Halo 4 UNSC or the Halo 2 Covenant in a straight fight. Which I don’t think is being established. They are of the moment and the result of circumstances.
Well, the Banished are in the market for genocide. They’re definitely no better than the Covenant. These are not innocent victims fighting the good fight.
The banished are very strong but different from other factions.
I think of them more like space Vikings, or space pirates. They are motivated more by riches, glory or just not bowing down to a king rather than good or evil. They are powerful no doubt but they lack the support structures many nations have. So they raid, pillage, and scavenge more than have goals like the UNSC or covenant or arbiters forces have.
Honestly I get the vibe that they’re becoming a cult to Atriox. They talk about his creed and vision a lot. He makes propaganda towers talking about their values.
Plus there might be something up with him. He seemed very, obsessed, with finding the secrets of the Endless.
It was mainly written that way because too many “fans” complained how OP it was in Halo 4, that the UNSC should always be on the defensive. So now it got nerfed to the point it gets ambushed and boarded to hell. Well, those “fans” got what they wanted. I hope they are happy, because I don’t.
Tell me when a UNSC in Halo Lore did get owned, much less boarded?
The Spirit of Fire has managed to hold her own in multiple encounters, even (somehow) going toe-to-toe with a Supercarrier.
Yeah it’s like one minute a capital ship is this enormous thing that takes time to chew through. In others it only takes a few minutes, for a bigger ship, fighting much smaller vessels than an assault carrier…. 
Plus in the books unshielded UNSC ships of that vintage tended to get one shotted by Covenant ships. The only way they won was by crazy tactics, speed and excessive use of nuclear weapons; not something you can do in a carrier.
It’s why I really don’t want the Spirit of Fire to show up because it will make zero sense if it’s magically able to walk through the Banished flotilla which we can see in the rings skybox.
I suspect 343 are probably going to do a canon fodder article explaining why this specific type of Banished ship is able to do this and is near useless at anything else at any kind of gun fight at range. Which allows them to handwave why the UNSC isn’t losing every space battle immediately from now on. Consider that the Pillar of Autumn is the same size as that chunk which gets ploughed through in the cutscene.