I ended up defeating mimikyu in one attempt. I basically paralyzed it with Magneton, then kept using night slash with the Greninja I got from the demo version on mimikyu and its ally pokemon. If Greninja got knocked out, I quickly used a revive, then kept spamming night slash.
I found the battle against Lurantis harder because only one of my pokemon was good against it, and Lurantis kept using Synthesis to heal itself. Lurantis would also summon a Castform which would use Sunny Day which made Lurantis practically completely heal itself whenever it used Synthesis. And because of Sunny Day, it would obliterate any of my pokemon with solar blade in one turn. I managed to get past it because my Rowlet was holding a quick claw which let it move first, so it defeated Lurantis before it used Synthesis.
Well I finished the game last week. Spent all day every day playing it. I kept using only decidueye for most battles, so it became overpowered and easily took out most pokemon. Overall, I really liked the game.
