Dio Brando is undoubtedly one of the strongest Stand users in all of JoJo's Bizarre Adventure. His Stand, The World, has about the same power, speed, and precision that Jotaro's Stand, Star Platinum, has but with the added bonus of being able to stop time. Dio's time stop ability is ridiculously overpowered, so he can probably beat just about any other Stand user, but there are also Stand users he probably can't beat, all Stands are created differently after all.
For this list, we won't be looking at Stand users Dio has already faced, so characters like Jotaro and Kakyoin won't be making an appearance. Here's 5 Stand users Dio can defeat (& 5 he can't)!
10 Can't defeat: Enrico Pucci
First up on Stand users Dio can't defeat is Enrico Pucci, one of Dio's most loyal followers and the main antagonist in Stone Ocean. Now, because Pucci's Stand has 3 different versions, for this list we'll be talking specifically about the final and most powerful version, Made in Heaven.
Made in Heaven doesn't have much in the way physical strength, but it is by far the fastest Stand in the entire series. It also has the power to accelerate time to the point that it created an entirely new universe. Dio would have no way of defeating Pucci because Made in Heaven would counter Dio's time stopping ability by accelerating his time limit.
9 Can Defeat: Jolyne Cujoh
First up on Stand users Dio can definitely defeat is Jolyne Cujoh, who happens to be the daughter of a previous JoJo, Jotaro Kujo. Jolyne's Stand, Stone Free, has destructive capabilities pretty much on par with Dio's The World and also has the versatile ability to turn itself and Joyle into string.
Jolyne would no doubt put up a good fight, but we just can't see any way for her to actually defeat Dio. At the end of the day, Dio's Stand is slightly faster, and Jolyne's string abilities would not likely be a match for Dio's strength.
8 Can't Defeat: Carne
Carne from Vento Aureo has a very strange Stand. His Stand, Notorious B.I.G., is fueled by Carne's hate and as such, can only show its true power after Carne dies. So Dio would be able to easily kill Carne, but that won't he's won. If anything, that's when the true battle begins.
Notorious B.I.G.'s ability is to absorb energy, latching itself to any object to eat away its energy causing the Stand to grow in size. Notorious B.I.G. could absorb energy from living things, Stands, and even automated objects like an engine. Oh, and it's also completely invincible. It cannot be killed. With all of Dio's power and abilities, there'd be no way from him to actually defeat it.
7 Can Defeat: Rohan Kishibe
Rohan Kishibe's Stand, Heaven's Door, may lack in destructive power but it more than makes up for it with its arguably overpowered abilities. Heaven's door has the ability to turn people into books, pages unfolding from their bodies. The pages of the book contains all the information and memories of the person in question.
Rohan has a chance to defeat Dio if he can use Heaven's Door before Dio can use The World, then write into Dio's book that he can't attack Rohan. But that doesn't seem likely. The World is faster than Heaven's Door, so Dio would be able to use Time Stop before Rohan can use his Stand. Since Heaven's Door is much weaker than The World, it'd be no contest.
6 Can't Defeat: Giorno Giovanna
Next on the list of Stand users Dio can't defeat is his own son, Giorno Giovanna. After piercing his Stand with the Stand Arrow at the end of Vento Aureo, Giorno's Stand, Gold Experience, turned into Gold Experience Requiem, becoming the most ridiculously overpowered Stand in the entire series.
Gold Experience Requiem has the ability to revert actions to the state of "zero", nullifying the action and preventing it from becoming real. Dio's Stand ability may be incredibly powerful but it means nothing against Gold Experience Requiem. Anything Dio tries would just be reverted to zero and cancelled out. Even physical attacks would do nothing to Giorno.
5 Can Defeat: Josuke Higashikata
Like The World and Star Platinum, Josuke's Stand Crazy Diamond falls into the "punching ghosts" category of Stands. Crazy Diamond has immense strength, perfect for punching criminals or plates of spaghetti, but that's not all it can do. Crazy Diamond has the ability to restore anything it touches to a previous state of being, though he usually uses it for healing.
As strong as Crazy Diamond is, it's unlikely Josuke could defeat Dio. Crazy Diamond could probably match The World in destructive power, but The World's ability to stop time coupled with the fact that Josuke can't use his Stand ability to heal himself means this fight goes to Dio.
4 Can't Defeat: Diavolo
Araki likes to give his main antagonists Stand abilities that manipulate time in some way, and Diavolo is no different. Diavolo's Stand King Crimson is immensely powerful and has the ability to erase time. It's a confusing Stand ability but basically, King Crimson can erase up to 10 seconds, during which no one but him are able to experience what happened. It just works, okay?
King Crimson's ability gives Diavolo the upper hand against Dio and his Time Stop. Dio can stop time for up to 9 seconds so theoretically, Diavolo would just have to use the precognitive ability of his sub-Stand, Epitaph, combined with King Crimson's Time Erasure to defeat Dio.
3 Can Defeat: Josuke Higashikata (JoJolion)
Josuke makes a second appearance here on the list, and as another Stand user Dio can beat, but this Josuke is vastly different. This Josuke is a fusion between two people, Josefumi Kujo and Yoshikage Kira, and his Stand is that of Josefumi, Soft & Wet. Soft & Wet doesn't have much destructive power but its plundering ability can be used in a wide array of situations.
Dio would have a tough time of beating Josuke, but he would definitely come out on top. Josuke can use Soft & Wet to plunder Dio's eyesight or the like, but Dio's vampiric healing would likely offset Josuke's plundering ability. It is worth noting, however, that Josuke's Stand has a huge amount of potential yet to be unlocked, so maybe one day Dio won't be able to defeat him.
2 Can't Defeat: Funny Valentine
Funny Valentine is the 23rd President of the United States and the main antagonist of Steel Ball Run. His Stand Dirty Deeds Done Dirt Cheap, or D4C for short, gives Valentine the ability to travel between parallel universes. Not only would Dio have to deal with Funny Valentine's dimensional ability if they were to fight, but Valentine would have another trick up his sleeve: Love Train.
Love Train creates a wall of light that redirects all misfortune, in this case any attacks, away from Valentine and sends the misfortune to a random place on Earth. Effectively, Funny Valentine is invincible when Love Train is activated, and we just don't see any way for Dio to get around it.
1 Can Defeat: Yoshikage Kira
Last on our list of Stand users Dio can claim victory over is Yoshikage Kira from Diamond is Unbreakable. Kira's Stand, Killer Queen, has the devastating ability to turn anything it touches into a bomb. Unfortunately, that ability would probably have no effect of Dio, who can just stop time before Kira detonates the bomb and defeat him.
Killer Queen's third ability, Bites the Dust, has the ability to create a time loop in order to protect Kira and would be the best ability to use against Dio, but likely only temporary. Dio is intelligent enough to break the time loop and defeat Kira. Failing that, Dio can just throw an ambulance at Kira.