Serperior was not holding a choice scarf but Rampardos was but how can Serperior outspeed Rampardos when Rampardos is holding a Choice Scarf and Serperior is not holding a choice scarf but I think leftovers. Is this a glitch?
Choice Scarfed Rampardos Max Speed :
Max Serperior Speed :
The Serperior either didn't have Maxed Speed or the Ramparados had a Speed Boost like Rock Polish. Trick Room might've been in effect but I highly doubt that
Serperior is fast. Rampardos is not. Probably the only way Rampardos could have outsped was if your Serperior had no speed investments and the opponents Rampardos had max speed and a Choice Scarf.
Word of advice- Never ever give Rampardos a Choice Scarf. Its speed is one of the worst imo. If this person you were battling was a friend tell them to try a Choice Band or Life Orb.
Hope I helped with this :)