Ok. Ill add trubbish to checking fairy and vice versa with gunk and foongus even though doesnt matter that much.
...yes it does? It looks really, really dumb. That's really, really, bad.
Reasoning for fighting types are in c&c, lists how they all beat it. And idk, steel types arent mentioned in c&c maybe because superpower is a main move.
That reasoning explains precisely how they all check it after it's gotten a kill. That's not a "great way to deal with deino" (even if they can take crunch and superpower.)
If steel types are not mentioned due to superpower being a main move, despite as you say it being 'hard to predict on a scarf set', well...
Let's examine fighting-types for a second. How are they switching in and answering deino 'greatly'? On the revenge, double switch, in on a favorable move. Now, in a double switch deino is free to superpower, but that's pretty prediction-based. If steel-types come in on a favorable move...
236 Atk Hustle Deino Outrage vs. 244 HP / 0 Def Eviolite Ferroseed: 7-9 (29.1 - 37.5%) -- 26.5% chance to 3HKO
(7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 9)
Without def evs, even. Gyro 2shots back. It can also take 2 crunches.
236 Atk Hustle Deino Outrage vs. 76 HP / 0 Def Pawniard: 12-14 (54.5 - 63.6%) -- guaranteed 2HKO
(12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 14)
236 Atk Pawniard Brick Break vs. 0 HP / 36 Def Deino: 18-22 (85.7 - 104.7%) -- 6.3% chance to OHKO
(18, 18, 18, 18, 18, 18, 20, 20, 20, 20, 20, 20, 20, 20, 20, 22)
Fine, it needs a bit of damage. At least it can switch in, though.
236 Atk Hustle Deino Outrage vs. 0 HP / 0 Def Magnemite: 12-14 (63.1 - 73.6%) -- guaranteed 2HKO
(12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 14)
240+ SpA Magnemite Flash Cannon vs. 0 HP / 36 SpD Deino: 15-18 (71.4 - 85.7%) -- guaranteed 2HKO
(15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 18)
So basically it switches in, takes one hit, and blasts back first. Sorta like...
196 Atk Timburr Mach Punch vs. 0 HP / 36 Def Deino: 14-18 (66.6 - 85.7%) -- guaranteed 2HKO
(14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 18)
Timburr wins on the revenge thanks to drain and can switch into crunch and superpower (losing half its life on super). On the other hand, magnemite needs a good bit less prior damage to start ohkoing.
Overall, steel-types can at least switch into outrage and KO or nearly so first, or take 2 and dish back damage.
Whereas fighting-types can only revenge or switch into lesser moves, or sometimes prio.
But yea, fighters are great. Steels! Pff, who needs them.
Not adding fire fang. Only does ~50% to cottonee not even worth it. Zen headbutt can reliably KO poison and some fighting types without worrying about fairies switching in.
I...i...WHAT?
236 Atk Hustle Deino Zen Headbutt vs. 212 HP / 196+ Def Eviolite Spritzee: 6-8 (22.2 - 29.6%) -- 85.9% chance to 4HKO
(6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8)
-1 236 Atk Hustle Deino Zen Headbutt vs. 116 HP / 196 Def Eviolite Snubbull: 5-6 (20.8 - 25%) -- 0% chance to 4HKO
(5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6
236 Atk Hustle Deino Zen Headbutt vs. 116 HP / 196+ Def Eviolite Cottonee: 6-8 (27.2 - 36.3%) -- 11.7% chance to 3HKO
(6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8)
Let's say you kill a poison or fighting-type with outrage. A fairy-type comes in to revenge you. Now, do you think 'what a bummer?'
No! You think, "holy shit, he had a hard wall and i still managed a kill!!!!11! Thanks, bad opponent! I mean, it's not like deino is a defensive virtuoso and it only revenges unboosted threats at 80% accuracy. It's a cleaner and smasher and it can't do either with fairies around, so why not 1 for 1 trade?
...by the way, it seems like you mean "revenge those mons", since i'm not switching to them if i have a fairy. That's kiiiinda okay for poisons, but why would you revenge fightings with a 72% accurate move on a pokemon that can't afford a miss and needs significant weardown and is hit se by any prio besides fake out they have?
Mienfoo: 14-18 (66.6 - 85.7%) -- guaranteed 2HKO
(14, 14, 14, 14, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 18)
Regenerator+drain punch, js. You do smash the LO set but this is way more common.
236 Atk Hustle Deino Zen Headbutt vs. 76 HP / 76+ Def Eviolite Timburr: 14-18 (56 - 72%) -- guaranteed 2HKO
(14, 14, 14, 14, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 18
Still has drain punch as main stab, mach punch for 66% minimum.
Croagunk, fair enough, though vacuun wave is really no fun for anyone.
So, to sum it up: zen headbutt is okay at revenging stuff you shouldn't even necessarily be revenging, barely okay at hedging, and will only really matter in situations where deino is deadweight anyways. Oh, and it has ~focus miss accuracy.
I really dont think its worth it to literally only hit cottonee, since its worthless for anything else. Not to mention its hard to predict on a scarf set.
236+ Atk Hustle Deino Fire Fang vs. 116 HP / 196+ Def Eviolite Cottonee: 10-14 (45.4 - 63.6%) -- 99.6% chance to 2HKO
See, here's the thing. If a fairy-type exists, as i mentioned, you are pretty much a non-factor. You kiiiiind of help defensively and maybe force out certain unboosted threats that trouble your team, but you give up constant free attacks or support moves in return. Maybe if you managed to kill said fairy you can sweep lategame, though that's a big maybe.
Cottonee, according to the june stats (the most recent stats i found, and i did search fairly hard), is used about 10% of the time. Now, maybe usage dropped dramatically since then, but it could've also risen, so, so let's stick with 10%. That means that in one out of ten battles, your deino is deadweight.
Unless you have fire fang, in which case you can not only take it out with good prediction, but pose enough of a threat to force a mispredict (likely after you scored a hit with fire fang though). Now, maybe you have a bulky grass that prevents it from healing, in which case zenbutt is okay, but you still want to kill it fast. By the way, predicting a mon that takes lol from half your moves and zero from a third is...still not easy, but definitely easier.
Of course, the real thing about zenbutt is that it lets you trash fighters on the switch-in without being lock-revenged by a faster scarfer. Still, if those fighters (or pzns i guess) are weakened, crunch, superpower, or fire fang (dry skin croa) can still 2hit. And if those moves can't, you can almost certainly outrage twice, which means a half chance of it ending. Which means the opponent sacced a mon for a half chance of revenging another. Only timburr, due to mach, and kinda croa, are changing this. (You can switch out of croa after fanging it and its wave isnt that strong.)
Now, outrage can miss when locked in. But, if the first misses you can switch out, so you only need to worry about the second one. And zen "focus miss" headbutt has its own missing problems. (2 outrages hit 64%, zen 72%. Lol.)
tl;dr most changes werent relevant or necessary
Tl;dr, and after that i bet everyone needs it...
Zenbutt is only mattering in odd situations where you're revenging stuff you shouldn't be revenging or hedging against stuff you can just outrage, and don't want to be locked in.
Fire fang gets past a true counter.
The changes are so necessary i can taste them.
By the by, it's kind of worrying that I provided better reasoning than you for your argument, especially since i've never used deino. This does NOT, in any way, come from a place of arrogance and is not meant to be insulting.
You're a fine writer and all, i just think you need a bit more metagame experience.