Dispelling Haste with Slow

Question

Haste and Slow are opposites of each other.

Our group got attacked by creatures under the same haste spell. Our caster responded by casting slow on them but due to their spreading out was unable to hit all the ones under the effects of haste, and also hit some that were not under the effect of haste.

Slow

Slow counters and dispels haste.

Haste

Haste dispels and counters slow.

We were unclear on exactly what happens. We came up with the following potential cases and were not sure which was correct

• The whole haste spell is dispelled and no other effect
• Haste is dispelled and others can be affected by slow
• Only the ones within the slow area are dispelled of haste or slowed

There is a related question which was dispel magic and multiple summons from the same spell.

Answer 1

Here the Pathfinder Core Rulebook FAQ directly addresses this issue:

Dispel Example: You are a 5th-level wizard, your opponent is a 6th-level sorcerer. On her turn, the sorcerer casts slow and targets 6 of your allies; all 6 of them fail their saves and are slowed. On your turn, you cast haste and target 5 of your allies; this automatically dispels (no caster level check needed) the slow spell on those allies, leaving them without the effect of slow or haste (your 6th ally is still affected by slow). Note that this does not merely suppress the slow effect for the duration of your haste—the effect is completely dispelled on those 5 allies. Note that it doesn't matter if the target would normally get a saving throw or spell resistance to negate or avoid the spell used to dispel (such as casting slow to dispel an already-caste haste); to speed up gameplay and prevent lopsided applications of this sort of dispelling, the "diametrically opposed" spell automatically dispels its opposite, regardless of the desires of the creature affected by the opposite.

Thus, in your case, after picking the targets of the slow spell, those folks who were affected by the haste spell automatically wouldn't be affected by the haste spell any longer and also wouldn't be affected by the slow spell, but those folks who weren't affected by the haste spell would make saving throws against the slow spell normally.