Assassination Classroom Vs. One-Punch Man

There's been a rash of surprising licenses from Viz lately.  Ranging from two Shoujo Vampire stories to
the once-thought unlicensable Master Keaton, due to the copyright conflict between Naoki Urasawa and Hokusei Katsushika, over whose name should've gotten top billing.  But the one that stood out was Assassination Classroom, which was once said to be too risky, considering the nature of students bringing guns to school in an attempt to kill their alien Teacher, who unlike the My Teacher is an Alien children books, makes no bones to hide his foreignness from his class.  At the time, it was thought to be too sensitive with the memory of Columbine being too fresh in people's minds.  But considering the once gun-shy country expressing outrage at being unable to bring firearms into coffee shops, and how the series relies less on long-distance weapons further on, the restrictions began to look rather pale in comparison.  The fact that guns are edited out of Anime is frankly, ridiculous.

A scene from the Storm story, "The Slayer of Eriban",
about a student from an Assassination school on his final exam

You would think that somebody who looks like a Smiley "Have a Nice Day" Face with teeth from Derek Kim Kim's The Eternal Smile wouldn't be much of a threat.  But as we all know, looks can be deceptive.  In Shonen Manga, the unassuming child can turn out to have planet-destructive abilities beyond the ken of mortal men.  Likewise, the perpetually grinning alien masks the extent of his destructive power and speed. While Koro-Sensei has designs similar to Nyarlathotep in eventually destroying the Earth, gleefully teaching students to learn how to kill him (despite their wasted attempts), his intent is more about inspiring his students to become better students by way of teaching them valuable learning skills independent to each individual student, working around their mental blocks and past trauma.

Can you tell the difference?

Since Assassination Classroom is in Shonen Jump, it stands to reason that a crossover with another licensed property, One-Punch Man, wouldn't be considered out of the question.  What's surprising is that a Doujin of this caliber hasn't been accomplished already.  It certainly would be something to see - a great fight between the strongest apathetic hero and the strongest Anti-Villain.

There can be only one winner - the audience.

Until then, you'll have to settle for this rough fanfic of what the match-up would most likely be.

(Saitama is roaming the outskirts of the country, until he comes across a ramshackle house)
Saitama: (knocks door) I thought I heard gunfire.  Is everything alright there?
Nagisa: (heard through other side of the classroom door) Oh yes, we were just starting class.  Nothing to worry about.
Saitama: (sounds unconvinced) Really.  Then you won't mind if I take a look?
Nagisa: No, wait!
(Saitama opens the classroom door)  (sees all the students with guns aimed at an alien octopus wearing a graduation cape and hat)
Saitama: (concerned) What are you doing?!  Are you trying to kill your teacher?!
Nagisa: Uh... yes.  that's kind of the point of this class.
(slightly embarrassed) Ah, well.  Sorry to intrude.  I'll be going now.

Koro-Sensei Notebook: Saitama's Weaknesses #1

He's extremely acceptable of outrageous situations.

Saitama: (changing his mind) No, wait, that's not right.  I came here because I heard news that there was a monster that was terrorizing the students here.  Would you know anything about that?
(All eyes in the class look towards the blackboard where Koro-Sensei is nonchalantly trying to appear inconspicuous, as inconspicuous as a smiling humanoid octopus can be)

(Saitama walks towards the teacher's desk where Koro-Sensei is simultaneously correcting the student's homework, taking attendance, doing flower arrangement, casual calligraphy and carving miniature Renaissance art on the side of a spent bullet shell)
Saitama: Can we talk outside?
Koro-Sensei: Certainly.  (Claps tentacles)  Free period everybody!  Feel free to think up impressive techniques to kill me!

(The two of them walk quite a distance until they come across an abandoned baseball field)

Saitama: You didn't have to go so far out of earshot.  It's not like I was going to yell at you.  I just wanted to understand what's going on here.
Koro-Sensei: Well, it's like this.  As you no doubt noticed, the surface of the moon has been obliterated, leaving a slim outline of its circumference, resulting in an eternal crescent moon is hanging in the sky.
Saitama: (Looks up at the sky where the remains of the moon is) Huh.  I never noticed that before.

Koro-Sensei Notebook: Saitama's Weaknesses #2

He's oblivious to the obvious.

Koro-Sensei: That was just a mere display of the extent of my powers.  I've given the Government one year to get rid of me.  In exchange, I'm training these lowly students in Class-E - the refuge for students considered to be beyond help in terms of educational advancement.
Saitama: (Presses fingers to bridge of nose) Wait, wait, back up a bit.  You're holding off destruction of the Earth unless one of your problem students manages to learn how to kill you before then?
Koro-Sensei: (Clenches tentacles in excitement) Nothing motivates you more than a project with a literal deadline.
Saitama: And what if somebody offs you before they have a chance to?
Koro-Sensei: They're welcome to try.  Though none have managed to succeed.  (Holds up pellet) So far, the only thing that can damage me are these harmless ball bearings -
Saitama: (holds palm up) Don't tell me your weakness right off the bat.

Koro-Sensei Notebook: Saitama's Weaknesses #3

Interrupts the speaker if they're talking for too long.

Koro-Sensei: Don't tell me you're going to try to kill me?
Saitama: (winds up shoulder) Well, that depends on just how formidable you really are.  You never know until you try.
Koro-Sensei: (Spreads tentacles out) And just how are you going to kill me?  A sneak attack?  An overhead laser canon?
Saitama: (Calmly walks forward) Nah, I'm just gonna punch you.
Koro-Sensei: (Chuckles inwardly) (Thinks) The fool.  He has no idea what he's in for.  He's going to experience humility on a scale that can't be measured.  I'll tease him a little first.  His head looks so lonely without any hair on it.  It could use a powdered wig.
(There's a quick imperceptible blur near Saitama)
Koro-Sensei: (Thinks) What was that?  It must've been my imagination.  Hmm?  That's strange.  (sees no wig on Saitama) I can't feel my limb?
(Sees his tentacle that was intended to play with Saitama has blown apart)
Koro-Sensei: (Stambles and falls back) (thinks) Wha-wha-wha-wha??? What was that???  He just blew away my tentacle apart in an instant???  And it's not regenerating?????
(A fly buzzes near Saitama.  He slaps and misses)

Koro-Sensei Notebook: Saitama's Weaknesses #4

He can't swat mosquitoes? (?????????????????????????????????)

Saitama: What's wrong?  I just barely brushed you.
Koro-Sensei: (thinks) It's BECAUSE you brushed me that I want to get away!!! (Escapes at Mach 20)
Saitama: (Easily catches up) Found you.
Koro-Sensei: IMPOSSIBLE!!! I'm moving at Mach 20!
Saitama: Oh?  I wasn't really paying attention.
Koro-Sensei: How fast can you go?!?
Saitama: No idea.  I've never been pushed that hard enough.
Koro-Sensei: (Panicking) (Thinks) Imma gonna fake him out with a buncha after-images! Each one in an individual attack pose!  I should be able to tell his fighting technique from how he fights each one!
Saitama: (Looks slightly impressed) Huh.  Cool trick.  Lemme try.  (Creates multiple after-images in front of each Koro-image, each one showing the exact same pre-punch stance)
Koro-Sensei: (Too shocked to think rationally) GNAFGEFSKAWA.  (Barely escapes intact)
Koro-Sensei: (Thinks) What's with this guy?? I can't read any killing intent off him, yet his punches are powerful enough to rip through my defenses like toilet paper!  I can't even smell any phreromones as to what he's going to do next!  Gotta contain him!
(Koro-Sensei extends remaining tentacles to restrict Saitama's movements)
(Saitama dodges and breaks apart the tentacles without hesitation)
(Koro-Sensei rockets up in the air)
(Saitama jumps up to where Koro-Sensei is)
Koro-Sensei: He's caught up to me already?!  Gotta go faster!!!  (Zooms away from Saitama in a hurry)
Saitama: (looks disappointed) He left the country.

(Out in the realm of the atmosphere)
Koro-Sensei: (Thinks) Gottagetawaygottagetawaygottagetaway!!!  (Zipping across multiple continents, looks behind him) Wait, he's not coming after me?  I don't see him anywhere.  Where'd he go?  Is he waiting somewhere in front of me??  (swings past Japan) Oh, he's still hanging in midair, slowly falling back to Earth.

Koro-Sensei Notebook: Saitama's Weaknesses #5

He can't fly.

Koro-Sensei: (Thinks) So he's not ENTIRELY Superhuman!  I can use this to my advantage.  Firstly, I'll spin around the Earth a few times to build up speed.  Secondly, I can compose my thoughts.  Thirdly, I can plan a counter-attack.
Note: [All of this takes place in a fraction of a second]
Koro-Sensei: (Thinks) He won't know what hit him!

(Saitama is looking forlornly up at the sky when he notices a  faint shining light coming closer towards him)
(It's an asteroid with Koro-Sensei's smiling face carved into it, with a handwritten note on the side saying "Love & Kisses, Koro-Sensei")
(The Koro-Asteroid is bearing down on Saitama at tremendous speed, burning up upon re-entry)
(Saitama easily and impassively smashes the incoming meteor to dust particles with a well-timed hit)
(Within the dust, Koro-Sensei covertly sneaks his way to Saitama's back)

Koro-Sensei: (thinks) I compressed myself to the size of a fly, and camouflaged myself on the meteorite's surface, all for the purpose of getting to his largest and most obvious weak spot:

Koro-Sensei Notebook: Saitama's Weaknesses #6

His cape.

(Koro-Sensei snags Saitama's cape from behind)
(Saitama instantly hits Koro-Sensei from behind)  There you are.

Koro-Sensei Notebook: Saitama's Weaknesses #6

His cape.
Scratch the cape!  He's full of openings, but they're all dangerous traps!  Stay as far away as possible!

(Koro-Sensei's tentacled body has burst apart like a spilled bucket of water balloons under a cactus)

Koro-Sensei: (Thinks) That didn't work.  Gotta keep my distance!  I'll figure out how badly I've been hurt later.  Uh?  Why is the ground getting in my way?  And it seems to be getting larger?  Oh, here it -
(Koro-Sensei prepares himself for a crash that never comes)  (opens his eyes)
(Saitama is standing calmly, holding Koro-Sensei's ruined body one centimeter away from hitting the surface)
Saitama: That was close.  You could've gotten hurt.

Koro-Sensei Notebook: Saitama's Weaknesses #7

He's too caring towards his victims.

Koro-Sensei: Why did you save me?  Didn't you come here to collect on the 10 Billion Yen reward?
Saitama: (Looks dumbfounded)  Ten billion?  Who needs that much money?  I'm just doing this for the challenge.  Let's wrap this up before the discount special day ends.
Koro-Sensei: (Looks shocked)  You buy discount foodstuff in the bargain bin too?
Saitama: (snaps fingers) You're the guy with the prosthetic nose at the Supermarket!  I was wondering if your face had plastic surgery or something.
Koro-Sensei: Uh... yeah!  You're the guy who's always wearing that weird-looking spandex costume in the shopping district!
Saitama: I'm still wearing the same costume.  And you didn't recognize me until now?
Koro-Sensei: I... thought you were somebody else with a similar fashion trend.

Karasuma: (who'd been watching the whole action taking place at the sidelines) (clapping sarcasically) Very clever, becoming fast friends with the man who beat you within an inch of your life.
Koro-Sensei: Uh?  Ah, yes!  That's what this was!  Buying time by finding common ground between yourself and your killer!
Karasuma: (whispering) He's totally covering up for his ineptitude isn't he?
Irina: So sad.
Koro-Sensei: That - that's not it at all!  I could fight back seriously if I really wanted to!
Saitama: Oh, so you CAN fight better than this?  I'm looking forward to next time.
Karasuma: (Gives Saitama the stink eye) Aren't you going to finish the job?
Saitama: I'm not going to steal your student's Finals project away from them.
Koro-Sensei: See?  He DOES understand!!
Saitama: Besides, I can tell that you're not evil.  If you really were a threat, you would've taken one of your students as a hostage.
Koro-Sensei: (Fumes) How dare you!  What kind of monster do you take me for?
Saitama: The kind of monster that could actually put up a good fight.  Besides, anybody who's frugal with their finances can't be all that bad.
Karasuma: (thinks) What kind of logic is that??
Saitama: If you do some exercise every morning, you should be able to put up a better fight next time.
Irina: (thinks) Don't encourage him!
Saitama: I'll be back in a month to see if you've improved any.  If not, I'll be having octopus stew for supper.  (wraps up fallen tentacles in a grocery bag)
Karasuma / Irina: (disgusted, thinks) You're not having that for dinner, are you??

Koro-Sensei Notebook: Saitama's Weaknesses #8

He doesn't discriminate on eating Octopus bal / Tenta / weird food.

Saitama: Well, if there's nothing else, I'll be off.
Nagisa: WAIT!!  How were you able to hurt Koro-Sensei like that??  We've never been able to even get close to him!
Saitama: (Looks at Koro-Sensei) Is it alright if I be your substitute teacher for five minutes?
Koro-Sensei: (gestures tentacle) Be my guest.
Saitama: Hello everyone.  I don't have much time before the bargain sale ends, so I'll make this short.
(turns to blackboard, drawing crappy stick figures worse than ONE's artwork)
Saitama: What you do is you raise your arm back, clenching your hand into the shape of a fist.  Then you thrust it forward towards your target with intent to hurt.  And that's all there is to it.  Any questions?
Entire class: (Thinks) TOO BRIEF!!!

Koro-Sensei Notebook: Saitama's Weaknesses #9

He can't explain his ability.

Koro-Sensei: It's true after all - those who can, do.  Those who can't, teach.
Irina: (whispers) Does that mean you can't teach these students to kill you properly?
Koro-Sensei: (miffed) Quiet, you.

Of course, this is possible too.