For Izuku Midoriya, receiving All Might's Quirk One For All has been a blessing and a curse. He possesses incredible strength capable of decimating the most formidable opponents and striking fear into the hearts of villains, it's just too bad that he risks harming himself whenever he goes over ten percent of his power.
As dangerous as his recently acquired Quirk is, it's not like he can pick a different Quirk. If he could, there are plenty of alternatives better suited to help him accomplish his dream. However, there are also plenty of Quirks that could prove detrimental to his safety and lifelong dream. Out of all the known Quirks exhibited in the show, there are five Quirks that would suit Deku better and five that wouldn't.
10 Better: Copy
As obnoxious as Neito Monoma can be, he's got one of the best Quirks in U.A. in Copy. His ability has only been seen during the Sports Festival, but it proved to be effective when it came to copying Bakugo and Kirishima's Quirk. Considering how meticulously Deku takes notes on everyone's Quirks, he could make use of their powers if he assembles the right team of friends.
He could train with them to master their Quirks and orchestrate strategies to make sure he can reach his teammates if the Quirk wears off. Hopefully, he won't get as big of an ego as Neito.
9 Worse: All For One
There's a reason that All For One is as feared by criminals and heroes alike as the evilest villain in the series. With his Quirk, he can steal the Quirks of anyone he gets a hold of and can harness multiple Quirks simultaneously. By most accounts, this is one of the powerful Quirks in existence, and, if Deku possessed it, he could take down any opponent with ease.
However, that would require Deku to take away someone else's Quirk and he could never bring himself to do such a thing without being remorseful for the rest of his life. Even if that wasn't an issue, there's still the matter of mastering all of his newly acquired Quirks.
8 Better: Blood Control
Part of what makes Deku worthy of wielding One For All is how he learned to use his powers in moderation. Channeling all of his power into one part of his body can take quite a toll, which is why he's spent so much time learning to use a fraction of his power and commissioned equipment that would better suit his Quirk.
Wielding Blood Control wouldn't be that different apart from trading pure power with controlling his exposed blood. If he can get a glove like Vlad King's, he could learn to release the right amount of blood needed to detain enemies and not suffer significant damage—provided he can stand the sight of losing lots of blood.
7 Worse: Bloodcurdle
In addition to months of training, Deku had to eat a strand of All Might's hair to inherit his Quirk. For a Quirk as powerful as One For All, that's a pretty good deal if it requires eating a single strand of hair once. Bloodcurdle, on the other hand, would require Deku to taste someone's blood every time he wants to use his Quirk and immobilize them.
Not only is it risky and disgusting, but it comes licking the blood of someone you don't know is bound to come with health hazards. He would also need to learn how to wield bladed weapons to make the best use of the Quirk.
6 Better: Fat Absorption
While Fat Absorption might not be everyone's first choice of Quirk, it's surprisingly fitting for Deku. It does require Deku to gain mass through unconventional methods, but it allows him to take punches and subdue enemies. Knowing Izuku, this Quirk would allow him to make more sacrifices than Captain America, but without taking nearly as much damage.
Not only would he keep a detailed diet and maintain a certain weight, but he could channel all his fat into a powerful counterattack without harming his body. Plus, he's more likely to win the hearts of people when he's smiling with chubby cheeks.
5 Worse: Sugar Rush
At first glance, Sugar Rush seems like an ideal Quirk for those that aren't looking for a crime-fighting career. The user can eat all the sugary food they want and wind up getting stronger as result, albeit temporarily. Ignoring the fact that this wouldn't give Deku the same strength as All Might, the sugar crash that comes after could make him a liability if the battle isn't over yet.
There's also the inconvenience that comes with him having to have sweets on-hand to use them in battle. Plus, anyone with that Quirk is likely to get sick of sugary food after a few weeks.
4 Better: Air Cannon
Air Cannon is among the many Quirks that One For All possessed during his fight with All Might. Although it's only shown briefly in the fight, it is capable of repelling a charging All Might and launch him backward.
Knowing Izuku, he could make great use of this ability to blast opponents and rubble away. If he uses his Quirk responsibly, he could even use it similarly to the Marvel character Banshee to channel his blasts beneath him to propel him into the air. The best part is that he would be less likely to injure his arms.
3 Worse: Explosion
There are several reasons why Izuku should not have Explosion as a Quirk. For one thing, it is a dangerous—not to mention kind of gross—Quirk that involves using nitroglycerin sweat to cause massive explosions.
Considering how nervous he gets, that's going to amount to a lot of sweat making him a ticking time bomb. More importantly, people will be comparing him and Bakugo more than usual, thus angering his hotheaded rival and resulting in Bakugo challenging him more to prove which of them is superior.
2 Better: Muscle Augmentation
The ideal Quirk for Izuku would allow him to protect the public offensively and defensively, which is why Muscle Augmentation might be the best alternative Quirk for the young hero. Instead of harming his muscles, he would have complete control over them just like Muscular, and he could make himself as strong as needed depending on the situation.
Not only could he pummel criminals with enough strength to smash cliffsides, but he would be durable enough to withstand the equivalent of One For All at 100%. Although the exposed muscle tendons might put off some people, there's no denying he would capable of reaching the Number One spot.
1 Worse: Meatball
In Izuku's defense, few people would be suited to handle the disturbing, non-sensical Quirk known as Meatball. It allows the user to manipulate others and transform their opponents into helpless clumps of flesh straight from the mind of David Cronenberg.
Even if he could master the unsettling Quirk, Izuku doesn't seem like the kind of person that would feel immense guilt from using it on people regardless of if they deserve it. Besides, it would be hard for him to rise in popularity when his Quirk would disgust the public.