since Deku's strongest suit is always speed, I'll just explain his speed amps and how they work for people who aren't knowledgeable of the verse.
To start, Deku is already a good perception blitz above his current 1.68c value at 100%, considering he should be at least somewhat comparable to the guy who completely blitzed and annihilated someone superior to the guy who did the 1.68c feat.
He has passive speed amps like Fa Jin, which works by stockpiling kinetic energy and releasing it all at once to get a massive increase in speed that can nearly statue things that he could BARELY keep up with even with a precognition-like ability giving him a heads up, and he did this at 45%. 100% would naturally be faster. Worth noting this ability can be charged with the slightest of movements like twisting and turning mid-air to dodge bullets. This was
calculated to be a 24x speed increase, and I know we're not allowed to calculate multipliers like this, but it should just go to show how broken the speed amp is.
The other passive speed amp isn't really an amp per-se, it's just Danger Sense. Deku has a 6th sense that can pick up ill-intent and react accordingly. It basically gives him a heads up to any attack as soon as the attacker even thinks of attacking. A villain once stole this ability from him (Shigaraki) and was able to pre-dodge an amped Deku who was essentially invisible to his eyes. The vestige behind this power was actively not cooperating which weakened its functionality, so Deku's version of Danger Sense would naturally be superior.
Then there's Gearshift, which allows him to increase or decrease the speed of anything he touches, while ignoring the laws of inertia and essentially being a shitty form of reality warping. He can use it on objects and even other people in Low Gear to completely slow them down to the point they're practically frozen from Deku's perspective. Or he can use it on himself to increase his speed to the point he can completely perception blitz and run circles on someone who was already comparable to Deku. This ability can also be stacked on top of itself, as Deku could use it to keep blitzing the same villain who had kept adapting to Gearshift's previous speeds.
And the last ability would be Black Whip. Deku can shoot out these black-and-green tentacles out of his body (that can stretch up to hundreds of meters or possibly even kilometers) that he can use either for mobility or restraining. But that's not important here. When Deku is heavily injured to the point he can't even move his limbs, he can run Black Whip through his own muscles and tendons to puppet himself even when he's barely conscious, which is called Overlay. Overlay is a pretty slept-on ability, as it not only acts as armor, but it also increases his speed to the point where he can match Gearshift's best and consistently out-speed the person who adapted to Gearshift's top speed.
The kicker here is that Deku can pretty much stack all of this onto himself to increase his speed to an ungodly amount. Granted, it's not something he'd open up with, but blitzing is one of his primary strategies when fighting strong opponents, so it's highly likely that he'd just keep increasing his speed throughout the fight, just like he did against Shigaraki, until he eventually starts statue-ing Cecilus.
If anyone wants the scans for all of this, i'll pull them up.
