I need something broken

[Urpriest]

Yeah I figured that out later haha

Also I'm assuming that since you're asking for a core class build, that goes for races as well so none of this pixie crap.

I would recommend druid as people have been doing, they are fun to play have lots of room for versatility. Since you are looking for earth shatteringly broken, they are a fairly powerful class at low and high levels, just make sure you take natural spell.

Pixies are core by any stretch of the imagination, unless core contains no monsters whatsoever.

They are tracked separately as opposed to stacking for a total effective level. There is nothing prohibiting you from making the same creature both an animal companion and a wild cohort. It's just specifying that you use the Wild Cohort chart for the Wild Cohort benefits, and you use the Animal Companion chart for the Animal Companion benefits, and that they are independent of each other and not the same ability.

You can dismiss your wild cohort and gain another one. You can dismiss your animal companion and gain another one. You can dismiss both and gain one creature to fill the role of both your animal companion and your wild cohort, provided that creature can fit within the restrictions of both.

Not only are they tracked separately, but it's explicitly an additional creature. Further, animal companions must be unmodified when chosen, so you have to choose it as an animal companion before choosing it as a wild cohort. Then the animal you're choosing for a wild cohort has bonus hit dice etc. The question then becomes, is it possible to gain a wild cohort with arbitrary bonus hit dice? If so, then just gaining a wild cohort with maximum advancement would be more effective, and could be done by any character.