WARNING: The following contains spoilers for My Hero Academia Chapter 331, "United States of America," by Kohei Horikoshi, Caleb Cook and John Hunt, available in English from Viz Media.
Even before Star and Stripe's debut, All For One praised her Quirk, New Order. It grants her the terrifying ability to assign a rule to any object she touches and names; the entire world is her weapon. With it in his possession, All For One claimed that the rest of his war on Japan would be just a formality, and Star continues to prove that this wasn't an empty boast. Her latest feat? Constructing what can only be described as a Susanoo from Naruto: Shippuden.
Star's Quirk isn't limited to affecting tangible objects. She proved this in earlier chapters when she literally removed the air surrounding the Shigaraki/All For One hybrid with the intention of suffocating them. When that strategy proved ineffective, she opted for an old-fashioned beat down and set a new rule for the air: "The air forms into my shape, but 1,000 times bigger." She uses the resulting avatar much like any Mangekyo Sharingan welding Uchiha would a Susanoo, pummeling Shigaraki with it from a safe distance. The similarities between these two abilities are unmissable, but how does Star's construct differ from the Susanoo?
The most noticeable difference between Star's construct and a Susanoo is that hers is invisible. Even though it's very much solid matter, it's made up entirely of air manipulated by her Quirk. This makes Star's Avatar a lot stealthier than a Susanoo. Its attacks are almost impossible to dodge since there's no way to tell where they're coming from. A Susanoo, on the other hand, is impossible to miss. Their constitution of brightly-colored chakra certainly makes them a lot more intimidating, but their attacks can literally be seen from a mile away. In stealth at least, Star's avatar trumps the Susanoo.
Star and Stripe's avatar is also much faster than a Susanoo. Its actions mirror hers, making it surprisingly agile despite its immense size. Its mirrored controls also allow it to cover a distance relative to hers instantaneously; if Star stretches one meter, her avatar stretches 1,000 within the same amount of time. The tradeoff is that Star is more vulnerable than if she was using a Susanoo. The creator of a Susanoo controls it from within and is sheltered in its most protected spot. In contrast, Star controls her avatar from outside its body.
The Susanoo has other advantages over Star's avatar. For example, each has powers unique to its owner. Madara's Susanoo was capable of creating projectiles he called the Yasaka Beads, and Itachi's had both the Totsuka Blade and Yata Mirror. Star hasn't yet been shown to be able to manifest weapons for her avatar, but given the blank slate nature of New Order, it wouldn't be entirely out of the question. Her avatar isn't perpetually unarmed though. She's already been shown to be able to grab lasers affected by New Order and use them as makeshift spears.
Whether or not Star would be capable of beating a Susanoo is unclear right now, but that's not her current assignment. So far, her avatar has retained the upper hand against Shigaraki For One, but their regenerative ability makes it impossible to safely conclude that they're out of the fight, no matter how grave their injuries may appear.
Unfortunately for them, Star and Stripe seems determined to push Shigaraki For One's regen to the limit. The chapter ends with her calling an airstrike on her foe. Should they survive the missile onslaught, it will be interesting to see what America’s number one hero comes up with next.