There are lots of classes that can be made to overwhelm in combat. If the primary focus of your Pathfinder game is combat, players will build their characters toward being effective in combat. Some players will do this better than others. Some classes are much easier to "break". Even at that, Pathfinder provides so many monsters with so many special abilities that a constant mix should be able to challenge even the most combat oriented character. They probably have some weakness. The character who is a DPS god probably doesn't have incredible AC, Fort, Ref, AND Will, along with improved evasion. A variety of monsters all at once means more for everyone to do; one mega monster, 6 archers and a caster (who is maybe even a summoner). If the combat dominating character is a caster, then throw lots of little encounters at them with no time to rest. I don't agree with gearing every encounter towards the "challenging" characters, this is what they've focused on so let them enjoy the spoils of their efforts, but you should definitely be able to design encounters that will (from time to time) neutralize those characters.
A good GM should be able to encourage character balance by throwing a variety of challenges at the players. Throw numerous social challenges at them. Once again, if one player has built their character to shine here, let them have their glory, but set up scenarios that will burn them if they put all their eggs in one basket, "Make a (challenging, but fair DC) diplomacy check to convince the dwarf king to aid you in your quest. Anyone, but the elven bard who, along with the other half-elf character, has not been allowed to enter the bigoted dwarf king's court." Set it up so the characters have to canvas the city to locate the NPC and convince them not to leave. If the characters spread out, the likelihood of locating the NPC will greatly increase, but the locating character will be the one responsible for making the social skill check.
Set up environmental challenges for the players. Dungeon environments are perfect for this. If the characters wish to advance they need to climb the cliff, jump the crevasse or swim the river. Setup encounters with overwhelming forces that they can't possibly win through combat, where the characters will need to talk their way out of, sneak past, or run away from. You can be a real @#$% and force them to swim the rapid flowing subterranean river, through the anti-magic field.
Limiting magic item availability will also make min/maxing less prevalent. If they can walk into any town or city and buy exactly what they need, it will make challenging them more difficult and will make them less appreciative of the random items they find. Sure they may be able to craft it, but then they're focusing on improving their crafting. You can also require therm to complete side quests in order to obtain their crafting ingredients. The book gives you price requirements for magic item crafting materials, but whoever said those materials were currently available for purchase in the character's town?
The short of it is, the more time the party spends in combat, the more they will focus on maximizing their combat capabilities. The more types of challenges the GM presents, the more balanced the characters will tend to be and the less need there will be to worry about which classes are inherently overpowered and can be abused.
