Question

I.e.
Deoxys speed form becoming paralyzed v.s. ferrothorn. Who will move first? And who will move first if Deoxys uses extreme speed?

Answer 1

Answering because the previous answer was incorrect.

Additionally, its Speed is reduced to 25% of its previous value (except for Pokémon with the Quick Feet Ability, where this condition raises the Speed by 50%).

It's only 25%. Deoxys-S has a max Speed of 504. Let us see what it is after:

504 / 4 = 126.

If Ferrothorn was running 204 Spd EVs with a neutral nature, nature, or 160 Spd EVs with a +Spd nature, Ferrothorn would outspeed a paralyzed Max Speed Deoxys-S.

If Deoxys-S used ExtremeSpeed, it would go first, as it is a priority move.

Source

Comments

wth you go ferro