You'd have to build in a killing technique, but here is the extreme defence:
The Immortal Mage Slayer Old Nixie: +3 LA +8cha, +6 dex, +2 int, small, SR:16+levels, DR: 5/cold iron, Dodge, weapon finesse
Cha: 42 [+16] (18 base +8 race +2 age +6 item +4 levels +4 tome)
Dex 26 [+8] (16 base -3 age +6 race +6 item +1 tome)
TOUCH AC: 87 (10 +16 monk +16 Duellist +1 size +5 deflection +16 profane +8 dex +5 Natural +9 armour +1dodge)
+2 AC whenever Foe misses
+4 vs AoO
+5 vs ranged attack 1/day
+4 vs 1 attack (Zephyr Dance)
+53 to all base SAVES. 1) Sword Sage (mobility) {Improved unarmed strike} {Dodge} {weapon focus} { weapon finesse}
2) Sword Sage Light armour
3) Paladin (heighten spell)
4) Paladin Cha-> saves, Deadly Touch
5) Hexblade
6) Hexblade Cha-> saves vs. spells (Versatile Spellcaster)
7) Hexblade Mettle
8) Hexblade Dark companion
9) Arcane Duellist Chosen weapon: +1 (Aesthetic Mage) Cha-> AC
10) Arcane Duellist Cha-> AC
11) Cleric Domains: Pride, Fate: uncanny dodge. Turn Undead
12) Cleric (Force of Personality)
13) Cleric
14) Mystic Wanderer Cha-> AC (Profane)
15) Wielder (FEAT)
16) Wielder Cha-> Touch AC (max=AC)
17) Witchhunter Cha-> saves
SAVESF2231 +4 +16 +16 +16 +5
R22 +8 +16 +16 +16 +5
W42312 +15+2 +16 +16 +16 +5
Manuvers:Zephyr Dance (+4AC vs one attack), Counter charge, Shadow Jaunt to avoid force cage + AMF combo.
Stance: Pearl of Black doubt (+2AC whenever Foe misses)