My Hero Academia has many characters that boast impressive quirks. From elemental powers to invisibility, both professional heroes and heroes in training have something meaningful to contribute when it comes to saving people. Class 1-A has made great strides in making their quirks more powerful and efficient, using their quirks to find creative solutions to their problems.
However, there are some quirks that are less than ideal, as they are too detrimental to the user or just plain gross. Even though many quirks are useful to hero work, there are plenty of quirks that fans would never personally want to have.
10 Stain's Bloodcurdle
Stain's quirk allows him to paralyze a target as long as he tastes their blood first. The length of paralysis is based on blood type. The blood types closest to his are paralyzed longer, while blood type O can recover the fastest. This quirk is less than ideal to have because it requires someone to get injured first. There are plenty of other quirks that are capable of subduing others that work more efficiently, like Shoto Todoroki's ability to freeze someone into place. Additionally, consuming someone's blood is a far cry from sanitary.
9 Mt. Lady's Gigantification
Mt. Lady is able to grow to the point of being taller than buildings. Unfortunately, this size can be a burden. She has gotten stuck between buildings before, and if someone is agile enough, they could easily (and perhaps literally) slip right between her fingers. With such a massive size, she has to be constantly conscious of her movements. She could easily hurt someone by mistake or destroy public property. In places with other people roaming around, it would be impossible to enjoy being giant.
8 Deku's One For All
Most of the time, using his quirk comes with horrible injuries. Deku's strength pushes his body past its limits, to the extent where he seems to have broken nearly every bone in his body at some point in time.
He even has permanent scarring on his hand to remind him of what could happen if he continues to push himself too far. If used carelessly, One For All is a destructive quirk strong enough to not only destroy its user but also decimate buildings.
7 Sir Nighteye's Foresight
Nighteye has the ability to see years into a person's future. This came with the consequence of knowing that this future cannot be changed. When discovering the tragic fate awaiting All Might, Nighteye had to bear the weight of knowing that there was nothing that he could do about it. This makes a quirk like this undesirable, as knowing when someone will die would make it difficult to enjoy life. Not many people could keep knowledge of the future to themselves, good or bad. This would make them a personification of spoilers.
6 Chewyee's Extend-O-Hair
Chewyee is covered with thick hair from head to toe. He can control this hair, and even make it grow longer. This must be like wearing a thick sweater during the summer, and must make taking a bath long and difficult. Getting clothes on must also be hard, akin to trying to wear four shirts at once. If this isn't bad enough, he probably sheds a lot as well. It takes a lot of work to maintain healthy hair, but he's probably spent hours keeping his presentable.
5 Lemillion's Permeation
Lemillion has the ability to become intangible, so he can go through any surface. When he does this, he unfortunately leaves his clothes behind, resulting in some pretty embarrassing moments. He states that his quirk was very difficult to master, mainly because of his quirk's biggest downside: when he's traveling through something, he experiences a sensation of falling. He also cannot hear, see, or breathe. A quirk that briefly robs a person of these senses would make this a pretty terrifying ability to many people.
4 Froppy's Frog Quirk
Although Tsuyu Asui makes having frog powers look really cool, in reality, they wouldn't be very fun to have. She can extend her tongue and use it to lift objects. Although she can lift people, it's not a very sanitary method of lifting and makes her tongue prone to getting injured.
Tsuyu can also store things in her stomach and eject them at will. She is very embarrassed by this part of her quirk and prefers that no one watch her do it.
3 Yuga Aoyama's Navel Laser
Yuga is able to fire a laser from his navel, powerful enough to blast through most objects. However, he isn't able to use it for very long, or he suffers from severe stomachaches. These stomachaches are usually so bad that it makes it difficult for him to move around much. It doesn't come with these consequences if it's used for a brief moment, but it's not worth using a quirk that will only cause the owner a lot of suffering.
2 Mezo Shoji's Dupli-arms
Mezo has tentacles attached to his arms that are able to grow additional eyes, ears, and mouths. These grown parts work more effectively than normal body parts. However, out of all of Class 1-A's quirks, this one is the least appealing to look at. It is a little disconcerting to see Mezo talk with a freshly grown mouth, and in reality, it might make people wonder where exactly they should be looking when he speaks. Although having enhanced hearing and sight is great in theory, there is usually no situation that requires two mouths or three ears.
1 Lego Quirk
Although the name of this student is unknown, his quirk seems to have turned his head into a flesh-colored Lego. The rest of him seems to be the body of an ordinary person, making fans wonder how he functions. Given that all he was doing was standing in the middle of the school assembly, this means that this appearance is common for him. Giving up eating and seeing does not seem like a fair trade-off for having a block for a head.