>>28983042I'm pretty sure increasing the speed stage of your pokemon has no effect on the crit chance. It's just based on their base speed.
If you want to try a really, and I mean really, over the top playthrough, you could repel trick on seafoam islands to get that nasty level 37 slowbro. At level 44 it learns Amnesia. Just give it surf and amnesia and it will beat sabrina without any trouble whatsoever.
But desu slowbro is very overpowered. Almost beats the elite four by itself without needing to heal in its low 50s. So if you don't want a pokemon that strong on your team thats fine too.