In Pathfinder there are a few spells that are effectively polar opposites, and as such have the text “counters and dispels [opposite]”. The rules for counterspelling are spelled out fairly well, but I'm not sure about the dispelling. If I use an opposed spell that would normally allow a saving throw and spell resistance to dispel its opposite, does that require a spell penetration check, allow a saving throw, or simply happen?
For example, the party is fighting a Wizard with Slow on his list. The party casts Haste. The next round the Wizard casts Slow on the party to dispel Haste. What rolls, if any, are required for the dispel to be successful?