1A/N: This was originally posted on Ao3, as a gift to a commenter, but I'm simply posting this here, just because.
Bakugou vs Karma
Bakugou enrages Karma by insulting Nagisa. That is the situation proposed. This matchup would end up in a landslide victory for Karma. With his high speed, reflexes, and combat ability, there is literally nothing Bakugou can do to counter him. Bakugou might be able to keep Karma on his toes with the explosions, but after having fought with Korosensei, Bakugou will seem hilariously slow to Karma. On top of that, Karma is proficient with traps. Traps would enrage Bakugou who does not have a keen eye for them. Bakugou would end up losing what little common sense he had due to his rage and Karma could spring a trap on him. If this was a friendly fight, it would end in defeat but since Bakugou made fun of Nagisa, Karma would probably try to skin him alive.
There is also the fact that Izuku had managed to keep up with Bakugou without OFA in the canonical battle simulation. Karma, without a quirk, is far superior and would not even have to try hard enough.
Result: Bakugou is killed by Karma, very easily. (Fun fact: Both Katsuki and Karma share the same voice actor.)
Mineta vs KarmaAs much as I would like Mineta to be beaten up, Mineta is rather proficient when it comes to using his quirk. For me, he is one of the smartest members of class 1-A and with enough confidence could be a good quirk analyst as well. That being said, much of this fight boils down to the fact of whether Karma has weapons or empty-handed. For the purpose of this fight, we will let him have a knife, which he seems to often have on his person (or he has it just for self-defense). Again, Nagisa is the reason for Karma's attack, so let's develop the situations first.
Situation 1: Class 1-A and class 3-E are meeting in friendly circumstances. When Mineta makes his remarks, he will not be ready for the impending doom to hit him right away. In that case, Mineta would not have enough time to react and would be smashed down, beaten up, stabbed, knocked out, etc.
Situation 2: Both are aware that they will fight. In this case, Mineta would make a minefield of his hair pops. Karma, due to his intelligence would know to avoid them since it is undoubtedly a bad idea. Through his speed, he would try to catch Mineta. However, because of Mineta's ability to bounce off the hair pops, it would be a strenuous task. But I believe Karma would be able to catch Mineta through the use of his own traps. Mineta also cannot keep producing the balls as it makes him bleed.
Situation 3: Mineta can win through luck or by chance. A stray ball that sticks to Karma, or Karma's own rare but possible hiccup could see Mineta steal the win.
Results: Mineta is a stronger opponent to Karma than Bakugou, but Karma is the most likely winner in this outcome. Mineta can only win through chance.
Any of the class 3-E girls vs MinetaClass 3-E have been trained as Assassins. All of them have the basic qualities of an assassin as well as excellent skills. Unlike Karma, who might try to fight Mineta right away, from the start, I believe the girls would hold back on their anger and prefer to have Mineta drop his guard before attacking him. While I did say, Mineta is a stronger opponent than Bakugou, it is only the case in open combat. Mineta lacks the battle skill, combat, and instinctual awareness of the danger that Bakugou has often showcased.
Results: The girls would win this by a landslide.
Class 3-E vs Class 1-A; quirklessDefinitely Class 3-A. None of the Class 3-E members have quirks and all of them rely on quirkless skills. On the other hand, class 1-A's quirkless ability is dismal. Ojiro being the strongest with his martial arts. Even Sato doesn't use martial arts (as far as I remember) and uses his quirk to power through. Izuku, while he was quirkless, didn't have good combat ability before meeting All Might. Even though he has met All Might now, he also got OFA. OFA has become his crutch right now as well. In terms of intelligence, he could try to put up a fight, but Karma can easily counter those as Izuku cannot rely on his classmate's quirks.
Results: Class 3-E wins.
Class 3-E vs Class 1-A; with quirk1-A wins this round. Class 3-E has spectacular powers, speed, and tenacity, but given the fact that Izuku, Yaoyorozu, and the other strategizers are allowed to work together and use their quirks, it would make things hard for 3-E. 3-E would not be able to rely on stealth as Jiro, Koda, Shouji, and Momo could monitor their movements and sounds. Todoroki can just instantly freeze all of them without a way to escape, Kaminari can just electrocute all of them. Hiding in the environment will be hard due to Koda's animals and the fact that Dark Shadow and Hagakure can team up to form a scout team. Kirishima is also basically indestructible and can ram his way through. Even if Nagisa attempts to use her supersonic speed, Izuku and Iida can easily match it up.
Results: Class 1-A wins.
Aizawa vs Karasuma; as a spar*Groans* This match-up is frustrating for me because I just cannot understand who would win. Aizawa's main ability is to erase quirks, basically taking away the villains' crutches. However, Karasuma is just a normal human. Both of them are trained in combat, have good reflexes, skills, and strengths. For this battle, Aizawa will have his standard equipment, and Karasuma will have access to blades (Since it's a spar, no guns.) Karasuma has had to train against Korosensei's insane speed, so one might say Karasuma has a speed or reflex advantage. But Aizawa has also shown the ability to keep up with Nomus (Even if in support.) At USJ, he was pummeled but still managed to stop Shigaraki from hurting his students.
Results: The fight is most likely to end in a draw. The winner (if there is one) would be the one who capitalized on his opponent's first mistake, whoever that is.
But personally, there wouldn't be a spar. Both of them would just decide the logical course of action is to not have a spar. Or Aizawa wouldn't agree to the spar in the first place and just get back in his sleeping bag.
Aizawa vs Korosensei; better teacherFor me, Korosensei is the better teacher by a long shot. He cares about each of his students and tries to accommodate all of them individually. Aizawa too is not bad, in fact, I would call it a draw except there are 2 glaring problems. The first is Katsuki and Izuku's relationship. You don't just ignore a kid saying he will kill everyone and always agitating and starting fights like a villain. Exactly what potential was in Katsuki!? That being said how did Aizawa measure potential. A teacher is supposed to build up the potential and train them. Aizawa expects as a teacher the potential to be handed on a silver plate.
Result: Korosensei
All Might vs KorosenseiKorosensei is much much faster than All Might. All Might may have super speed but he isn't fast enough to fly to the USA and back to Japan in such a short time. However, Korosensei doesn't have brute strength and his punches are not that strong. Korosensei cannot bide his time just by dodging around as All Might has enough endurance to keep up for a long time (assuming his injury isn't there) On the off chance Korosensei gets hit, he can just regenerate. It would be a game of tag.
In the end, Korosensei would win. Through his Mach-20 speed, he can just body slam All Might, use his tentacles, and stretch them out before moving so fast that the resulting hit is extremely painful and stinging (whiplash effect; basically what Luffy does in gear 2 but much faster).
All Might can try to create wind storms to keep Korosensei away but Mach 20 speed is more than enough to go against the wind. Korosensei can also stretch his tentacles to catch All Might and stick him to the tentacles and then he can just drown him. All Might would try to fight back but Korosensei can hold All Might underwater for the 1 minute needed. Alternatively, Korosensei can just travel to a hospital, get chloroform, get back and hold it under All Might's nose.
Next part: Read only if you have read manga or If you have no problem with spoilers.
Theoretically, the reason Izuku was able to unlock the previous users' powers was that he was in danger. In a case of mortal danger against All Might, OFA might also reveal their powers to him. In that case, through the help of danger sense and super speed from the predecessors, All Might could land a punch on Korosensei's heart, killing him.
Bitch sensei vs Midnight; better honey trapMidnight has never been shown to be a honey trap in canon or any fanfics I have read. While her behavior says otherwise, she does not have professional skill in it like Bitch Sensei. As a pro hero, she also shouldn't be a honey trap as that would not bode well with the public. I choose Bitch sensei for this one
Korosensei vs AFOEntirely depends on what quirks AFO has. If he has a quirk that allows him to travel at the speed of light, there isn't anything that Korosensei can do. Even in the manga, we do not know the extent of the quirk All For one possesses. We do know that the high-end Nomu is very fast, but are they as fast as Korosensei? The main thing Korosensei has an advantage over AFO is his speed but as seen with Gigantomachia and the high-end Nomu, AFO very likely has a quirk that gives him speed equal to that of Korosensei.
Result: I believe AFO would win. Even if AFO can't match Korosensei in a head-on fight, he has plenty of Nomu for support. On top of that, AFO is good at brainwashing with his ideals and could perhaps do the same to Korosensei