Here are some 2HKOes against imporant defensive Pokemon that you achieve with Reckless:
- 252+ Atk Life Orb Reckless Emboar Flare Blitz vs. 252 HP / 252+ Def Hippowdon: 208-246 (49.5 - 58.5%) -- 64.5% chance to 2HKO after Leftovers recovery
- -1 252+ Atk Life Orb Reckless Emboar Flare Blitz vs. 252 HP / 252+ Def Landorus-T: 165-196 (43.1 - 51.3%) -- 57.4% chance to 2HKO after Stealth Rock and Leftovers recovery
- 252+ Atk Life Orb Reckless Emboar Wild Charge vs. 252 HP / 252+ Def Slowbro: 221-260 (56 - 65.9%)
- 252+ Atk Life Orb Reckless Emboar Flare Blitz vs. 252 HP / 252+ Def Thick Fat Mega Venusaur: 203-242 (55.7 - 66.4%) -- guaranteed 2HKO
All those calcs are very important. Getting walled by one of the best physical walls in OU is obviously not fun (Hippowdon), and same goes for RestTalk Lando-T or max Def Lando-T in general (which is a viable stall mon). Also, by doing ~60% to Slowbro with Wild Charge, it means that you almost don't have to predict the switch-in anymore, as long as it has 10% residual damage on it and SR is up. Finally, the extra damage against Mega Venusaur means that it is much harder for it to stall you with recoil to death by spamming Synthesis.
Btw, i am talking about a 4 attacks set with Flare Blitz, Superpower, Wild Charge, Sucker Punch, Adamant, max Atk / max Spe, and LO, as this would be its best set with Reckless. Having a strong priority move to use at will against offense is one of the pros of Emboar as a wallbreaker, so you can't take this away by using CB.
And of course, there are a dozen of OHKO/2HKOes that you get with Flare Blitz and/or Sucker Punch that you couldn't without Reckless, but i won't go through details as what mattes more is its power against defensive Pokemon.
Finally, Malamar has a thread because it's a new Pokemon, and it's only logical to allow people to discuss about new Pokemon somewhere don't you think? At least until the tiers they belong to are formed.