not counting Merlin, who can teleport I would say
Well, the comparison will be a tad hard considering speed is not as much of thing in this manga as it is in others. The fastest sin seems to be ban. However even with an overwhelming advantage its not like meliodas actually had the short end of the stick. At least we can make the case that having a speed advantage is not enough to give you an overall advantage so to speak as would be the case in other manga. At least in their base form it does not seem like any one sin is even superior or inferior to the others which is weird considering what we know about ban and meliodas and about their power levels in the relevant areas.
How fast do you think ban and king can be easily justified?
Reflex wise, Ban is probably the fastest Sin. Otherwise, Overlord's list seems good enough. Diane is probably faster than Gowther though. The best speed feat was probably in the Motionless Man chapter, where Mel, Ban, and King kinda blitz Dawn Roar in under half a second and at a distance.
The best speed feat period though is Galan's dodging Merlin's spell.