I need something broken

[Kalaska'Agathas]

Read the last sentence again - he said core class build.

So he did. If that does indeed mean using Core only (I'm not convinced it does) then I would recommend Druid 20 with Natural Spell as I previously mentioned, or if you prefer (as I do) Ultimate Arcane Power, then the following build is what I would recommend:

Human Diviner 5/Red Wizard 10/Archmage 5, banning Enchantment and eventually Evocation. Take leadership, and have your cohort follow the same build. Then, by using Simulacrum, you (ab)use Circle Magic to cast level 20 spells at Caster Level 41+, while your Cohort does the same, and while your Simulacra of yourself do the same. Congratulations, now things need to make DC 36+ saves against all of your spells, you can dispel anyone (well, anyone not using the same trick), and you use the normal Wizard "I win" spells to win the game. All in Core.

Edit:

I don't consider monster races as a core race, even though they are contained in the core three books, I should have specified.

If I were a DM, I would not allow something with greater invisibility on, I mean really? GREATER INVISIBILITY, that opens doors to fun draining.

If I'm not mistaken, that is part of what the OP wants.