Mega Arcanine

Yep. We’re giving the goodest boi a Mega.

Arcanine, upon Mega Evolving, gains the Fairy typing. Its Ability is now Pixilate.

Its stat spread is now 90/160/80/110/80/135, making for a fast physical attacker, just like its base form.

To compensate for its lack of STAB and coverage, Arcanine now also gets Spirit Break and Headlong Rush, along with the new move Fairy Jaw, which is a Fairy type Jaw Lock.

A few calcs…

252 Atk Arcanine-Mega Close Combat vs. 252 HP / 52 Def Garganacl: 234-276 (57.9 - 68.3%) -- guaranteed 2HKO after Leftovers recovery

252 Atk Arcanine-Mega Close Combat vs. 4 HP / 252 Def Blissey: 604-712 (92.6 - 109.2%) -- 56.3% chance to OHKO

252 Atk Pixilate Arcanine-Mega Extreme Speed vs. 0 HP / 4 Def Raging Bolt: 396-468 (101.2 - 119.6%) -- guaranteed OHKO

However, some mons can still outspeed and OHKO, or live a hit and OHKO. For instance, ExtremeSpeed only 2HKOs Araquanid, while Surf cleanly OHKOs. Same situation with Ting-Lu and Earthquake OHKOing.

Basically, Mega Arcanine is a mon that wants to do a whole bunch of damage, but crumbles to any strong attack. I see this being in OU, maybe UU.