Dragon/Ice -> Dragon/Ice
Pressure -> Refrigerate
New Moves: +Bulk Up, +Nasty Plot, +Cosmic Power (Kyurem forms can’t use these moves)
125 -> 125
130 -> 155 (+25)
90 -> 110 (+20)
130 -> 155 (+25)
90 -> 110 (+20)
95 -> 105 (+10)
Flavor Concept: Kyurem’s body is said to be frozen, so Refrigerate is a perfect fit. Dragon Dance was deemed to OP, so I'm giving it Bulk Up. Some Pokemon learn Bulk Up, like Dialga and Gogat, that don't have the humanoid build, so Kyurem getting it doesn't break any huge flavor concepts. Kyurem is said to be harmful to humans, it even eats them at night (!), so Nasty Plot is consistent with flavor. Cosmic Power makes perfect sense for Kyurem because it is an extraterrestrial Pokemon. According to its legend, it comes from a meteorite and it landed on where the Giant Chasm currently is (Also where Clefairy line, Solrock and Lunatone live).
Competitive Concept: MegaKyurem is a scary mixed attacker, with access to an array of useful moves. As a set up user, it puts most other BU and NP users’ bulk to shame, with 125/110/110 and Roost. While its Refrigerated Hyper Voice is weaker than MegaGardevoir’s, it is faster than it and can readily get a +2 with Nasty Plot. Bulk Up allows it to be even more bulkier on the physical side while also being able to set up to sweep. At +1 defense, 0 HP/0 Def MegaKyurem gets 3HKO'd by a max attack MegaScizor's Bullet Punch, and at +1 attack, an Adamant set 2HKO's 252 HP/0 Def MegaScizor with Return. MegaKyurem can also run a more defensive-focused set, with Cosmic Power and Roost.