>>20752885>252 Atk Life Orb Lucario Zen Headbutt vs. 108 HP / 104 Def Conkeldurr: 190-226 (50.2 - 59.7%) -- guaranteed 2HKO>152+ Atk Iron Fist Conkeldurr Mach Punch vs. 0 HP / 4 Def Lucario: 228-270 (81.1 - 96%) -- guaranteed 2HKO, chance to OHKO after LO damageFor the record, the wonky Conkeldurr EVs are from what Showdown is calling the definitive AV Conk set for doubles. Obviously, Drain Punch is an OHKO.
Here's the Trick Room Conkeldurr set, scaled to level 50:
>252+ Atk Life Orb Iron Fist Conkeldurr Mach Punch vs. 0 HP / 4 Def Lucario: 164-195 (113.1 - 134.4%) -- guaranteed OHKO>252+ Atk Life Orb Iron Fist Conkeldurr Mach Punch vs. 0 HP / 4 Def Mega Lucario: 135-164 (93.1 - 113.1%) -- 62.5% chance to OHKOUnless you've got Screen support, Conkeldurr is best avoided altogether.
Also, a neutral STAB Close Combat is stronger than a Super-Effective Zen Headbutt.