I want to humiliate my group using a level 15 evoker wizard, and I was thinking Evoker2/Master Specialist 3/Incantatrix10. Banned schools would be illusion, enchantment, and necromancy. In combat, the only offensive spells cast, besides a greater dispel magic or two, would be evocations.

I'm thinking of metamagicking force missile out the wazoo, and using that to level the party, once member at a time. With CL 16 (easy), that's 4 2d6 missiles. Twinned, maximized, empowered, and repeated is 4*(48 + 0.5*8d6) over two rounds, or an average of 304 saveless damage. That should kill any party member on the first hit, and the party tank on the second hit.

With a familiar, and a quicken, that should be able to kill at least two party members in their first go.

How would you feel if this strategy was used on you? You have a reasonably optimized character (persistent metamagic abuse, over wealthed, gestalt, 40 point buy) that is level 13.

Another option would simply be using cone of cold or something with a similarly high damage cap on the dice that would kill even on a successful save.