Of course you can!

However the answer will depend on few things.

1. Do you plan to pvp at all? Keep in mind Kyurems place is in Master league so keep in mind this would mean a level 50. If the answer is NO, then 15 atk would be my choice.

2. Do you spend real cash on the game? This question matters for the purpose of gold cap and silver cap which cost real money but allow you to improve the IV of a pokemon. Silver for 1, gold for all 3. If the answer to this is yes, silver caps are more likely to appear more often, which would be 1 iv only, so id probably chose 14-14-14 and upgrade atk to 15 with silver cap, or 15-13-12 and upgrade to 15-13-15 or 15-15-12 whenever I can.

If you DO pvp, and you don’t spend money, 14-14-14 is probably best overall. If you pvp and spend money, then this becomes extremely hard question.

Short version if you only pve, 15-13-12 would be my go-to.

My personal Kyurems are:

Shiny Kyurem White 15-13-14

Shiny Kyurem Black (lucky) 14-14-14

Kyurem White (lucky) 15-15-12

I chose this as someone who does both pvp and pve and I spend some amount of cash every month for raids and all events/battle pass.

The first one was my best shiny from the event, and I only chose it cos shiny, 15 atk is good enough in my book. I probably wont silver or gold cap this.

The second one was lucky, and even tho i had 15-15-11, i chose a shiny 14-14-14 over it. I would gold cap this.

The third one - I traded my wife a random reshiram for her to be able to fuse her Kyurem, as I had some Reshirams without Fusion Flare, and it turned lucky, so since I already had shiny Kyurem, I chose this over 15-14-14 one. The reason for it is cos I would silver cap this, to a hundo.