That...depends heavily on which Jotaro your talking about? We talking about Part 3 Jotaro, Part 4 Jotaro, or Part 6 Jotaro (Pre-coma or Post-coma Foddertaro)?
If it's part 3 Jotaro, then...King Crimson gets blitzed pretty badly... Wait, here me out first before you say anything... My part two to my second CRT, if it actually passed, would've explained that the Silver Chariot vs Diavolo feat out in detail. Of course, due to Silver Chariot slicing at Diavolo and him disappearing, then attacking Polnareff is, at least on paper, an easy MFTL feat. However, all isn't exactly how it seems...
Not a member of the calc group, so take this interpretation as you will. Also, mainly focuing on the anime, not the manga, so...
Polnareff summoned a prime Silver Chariot, because of the unknown amount of adventures he went on with Jotaro after Part 3, while injured to try and attack Diavolo as they neared the end of their first meeting. We know this is a manual usage case due to the complexity of the actions Silver Chariot is performing and the lack of any commands from Polnareff like "There!" or "Now!". Eyeballing it with the ever-trusty framebyframe website, it appears that Diavolo and Polnareff are about...5 Polnareff's away from each other. Throwing that into a calc I somehow deleted so I can't copy it here, and counting off the second it took for Silver Chariot to move infront of Diavolo. That's around ~subsonic speeds for Silver Chariot in this instance, but that's just off eyeballing, so again, take that as you will. Looking at the sword swing, it's about a meter or so that Silver Chariot swung his sword in 0.01 seconds or 10 milliseconds. That's again... around subsonic speeds. Now, that's not impressive at all, nor is basically gouging out Polnareff's eye due to the fact we know King Crimson's ability commonly leaves people who experience it for the first time disoriented and confused by it's own nature. Attacking Polnareff again to mortally wound him before Silver Chariot can retaliate is a little impressive, but finishing somebody off after they're already badly wounded kinda downplays this a little. Now, you might be asking.
*Didn't Diavolo preemptively activate his ability mid-swing from Silver Chariot?
No, he activated it while Silver Chariot was coming upto him, far before the stand actually swung on him with it's rapier. I don't know if this is the case in the manga due to the obvious lack of movement, but it is in the anime, so correct me if I'm wrong in the manga's case, but King Crimson's ability does have a bit of startup lag early on in the anime. Shown during Bruno's short battle with the stand especially, Sticky Finger's fist doesn't actually go through his head until the long red flashing is fully off the screen, indicating his ability is fully activated. This specific red flashing across the screen gets cut down to a quick blip even in the time skip Diavolo used right after he gouged out Polnareff's eye, so I don't know what happened her specifically. Diavolo got extremely lucky though, becoming intangible the literal millisecond before Silver Chariot's sword would've dealt a fatal blow to him. Anyway, Diavolo obviously time skips and cuts Polnareff down to size, ending their first actual encounter battle.
*Well, even if this doesn't look great, we still have Diavolo's first-class speed statement, right?
Yeah, we have that, but we also have the implied information from the actual battle leading upto what we see of Diavolo and Polnareff. What do we know, you might ask?
1. This was a long and drawn out battle, no doubt about that. Polnareff and Diavolo both got to the cliff, more a feat on Polnareff's part for evading King Crimson until then due to said "first-class speed", but more on that later.
2. When Diavolo appears, he 100 percent intends to kill you in person. There's no real debate on this, if Diavolo shows up in person, he fully intends on ending your life himself ASAP. Not a point really, just a little fact he even states himself directly.
3. Diavolo nor King Crimson have taken a lick of damage from this "fight", so THIS MUST MEAN that King Crimson successfully evaded Silver Chariot's blade while wounding Polnareff directly. Of course Polnareff was fighting for his life, and didn't just let Diavolo outright harm him without trying to attack back. This feat is all the more impressive when you consider point 4.
4. DIAVOLO DID NOT ERASE TIME ONCE before actually erasing time to get behind Polnareff to finish their fight. This is proven when Polnareff quickly understands that Diavolo's skipping time, good job Polnareff! Didn't save you from getting crippled, but still... In any case, Polnareff never notes that he skipped time again or he dissappeared AGAIN. Before somebody brings up Epitaph more than likely predicted Silver Chariot's defensive swings while they fought. Epitaph, when used in a direct fashion without time erase accompanying it, is USELESS unless you have the necessary reaction speeds and movement speeds to avoid attacks. If an attack occurs before Diavolo can even perceive it, or before Diavolo can understand the vision Epitaph provides and act accordingly, he's basically shit out of luck.
5. Diavolo, although showing no real reaction at all to his arm being sliced, WASN'T able to come out of the darkness to attack Polnareff before Silver Chariot made it's own move. I'd say Silver Chariot was definitely automatically controlled in this moment due to the specific simplicity of the action, and the speed at which it was performed as well as Polnareff's own command in the form of NOW. This would be MFTL for reference. While luck WAS definitely a strong factor here, even by Polnareff's own admission, requring he spot Diavolo within an extremely, extremely short time frame before he could use King Crimson to attack. Like Where's Waldo, but for your life... Moving on, Diavolo compliments Polnareff on his speed before giving him a good-ole Superman high-five just like Joker got in Injustice. Where was I at, oh yeah. So, Diavolo, while among the fastest stands, shouldn't really be categorized among the absolute fastest of the verse like Jotaro, DIO, and Silver Chariot when it's being automatically controlled. An entire part upscales off him after all, so...I was actually thinking he should probably be moved down a couple tiers... Definitely FTL due to the statement of being in the top-tiers, as well as what I explained about his first encounter with Polnareff.
Reading this back, I just realized that I really wrote out an entire CRT's worth of information... Wow...