These are the strongest un-staged STAB Steel attacks vs uninvested eviolite Kyurem
252+ Atk Adaptability Mega Lucario Iron Tail vs. +1 0 HP / 0 Def Kyurem: 380-448 (97.1 - 114.5%) -- 81.3% chance to OHKO
252+ SpA Choice Specs Dialga Flash Cannon vs. +1 0 HP / 0 SpD Kyurem: 350-414 (89.5 - 105.8%) -- 37.5% chance to OHKO
You'll need SE attacks or strong boosted ones, luckily it's fairly vulnerable to hazards and has 5 weaknesses.
There's also definitely some offensive pressure here as well, most things that don't end it in one blow will take considerable damage.
