I was battling and a Galvantula paralyzed my Ferrothorn with Thunder, so I thought of this, since being paralyzed makes you slower.
No it doesnt
With no para
0- Atk Forretress Gyro Ball (46 BP) vs. 244 HP / 0 Def Sylveon: 116-140 (29.5 - 35.7%) -- 34.2% chance to 3HKO
With para
Source: https://pokemonshowdown.com/damagecalc/