Sollir, Wiz 5/Incantrix 10 (Magic of Faerun)/Archmage 5 (FRCS), chosen abilities: Spell Power +1-3, Mastery of Elements, one other choice.
Spells Active, Hide Life (9th, Tome and Blood), Arcana Form (9th, Book of Eldritch Might)-made persistant by Incantrix ability, Shapechange into a Spell Weaver (Creature Conversion Catalog thingie), Magic Tattoo (FRCS) x3, chosen ability being +1 spellcaster level all 3 times, Mark of Death (8th, Book of Eldritch Might)-makes you immune to death effects and have a death ray, Greater Contingecy (Tome and Blood) vs. Mordekainen's Disjunction, Greater Spell Flow (or something like that from Book of Eldritch Might).
Items: Ring of Speed (Constant Haste-there was one made by WotC), Animated Large Shield of Greater Fortification (and Spellcasting, if your DM insists you still get arcane failure chance), Headband of Intellect +6, as well as whatever other standard wizard gear you want (Rods of Greater Maximization, Empowerment, etc....) as well as some backups in case of mordekainen's disjunction
Feats in Particular: Spellcasting Prodigy, Spell Penetration, Greater Spell Penetration, Tattoo Focus (can be gained by a high level red wizard w/o expending a feat I believe), several Spell Focus and Skill Focus (Knowledge) for Archmage requirements, Iron Will for Incantrix. (Some feats can be gained by items that bestow them)
What this all means: You cannot die if you're reduced to -1,000,000 hitpoints (Hide Life), you can cast memorized spells without expending spell slots-thus granting you infinite # of spells/day (Hide Life+Arcana Form), in an Antimagic field instead of dying due to your negative hitpoints you vanish instead until the antimagic field moves away (Arcana Form), you cast 4 spells of up to 9th level and 1 more up to 6th level a round, every round, of the whole day (Shapechange+Haste and then a Quickened Spell which is reduced to +3 levels due to the Improved Metamagic ability of the Incantrix), being immune to damage, you are also immune to death effects (Mark of Death), Vorpal Weapons (Greater Fortification), most spells (you can cast Elemental Immunity-Tome and Blood- 5 times).
Strategy-Timestop, Meteor Swarm x3 (whatever element you choose), Distentigrate x1 the first round, then Meteor Swarm x4 (whatever element you choose), Distentigrate x1 during the timestop, rinse, repeat, if the monster is immune to all elements, use horrid wilting (if not immune), or worse comes worse, Timestop, Maze on target then Gate x2 followed by quickened mass haste on the creatures, repeat for the following rounds gating x4 then quickened mass haste or some other buffing spell to kill. You have a +34 caster level vs. SR and your DC is decent though not exceedingly high-but that doesn't matter since you can cast your spells so much and as much as you want for the rest of the day. The receptacle for Hide Life is hidden under the same way I posted a while ago on the best place to hide your phylactery but assuredly it takes over 5 years to get it
Edit: Or, if you get first strike
Shapechange into a Blackball (Creature Catalog Conversion thingie), Haste, Quickened True Strike, slam attack (made at around +30 or so melee touch)-if successful, your opponent is dead as if hit by a sphere of annihilation.
