Great Smiting 8 = 225 damage on smite vs. evil. This damage crits, and on a keen scimitar threats occur from 12-20, for 450 bonus damage vs. evil per crit just from smiting.Paladin 17/CoT8/Harper PARAGON5
Human, Charisma Gift, 20 starting CHA, Str 14, Dex 8, Wis 12, Int 12 (Gift, 14), Con 8
1-5 Paladin +1 CHA Weapon Focus (Scimitar), Alertness, Iron Will
6-10 Harper Paragon Expertise, Extra Smiting +1 CHA Divine Shield, Divine Might
10-19 Paladin Improved Expertise, Blindfight, Improved Critical (Scimitar), +2 CHA
20 CoT +1 CHA 25 CHA +18 BAB
21: CoT: Great Smiting 1 & 2
22: Paladin
23-24: CoT: Great Smiting 3 and 4 26 CHA
25-27: CoT Great Smiting 5 and 6
28-29: CoT Great Smiting 7 +1 CON (9)
30: Paladin Great Smiting 8
+12 Str and +12 Cha gear = +14 CHA bonus and +8 Str bonus, with divine might, for another 44 damage on crit smite. +3 (greensteel) brings it up an extra 50, for 500 bonus damage on crit vs. evil, before other sources of damage bonus.
And the +14 CHA bonus to Attack Bonus from smiting vs. evil bypasses the +20 attack bonus stacking rule.
You also get +14 ac from divine shield capping out your dodge bonus at +20 with a haste + mage armor and +1 ac on your boots, on top of improved expertise, full plate, and tower shield.
You can subtract 50 total smite damage off of a critical smite in exchange for one more point of wisdom through an epic feat, which will bring you access to Paladin 4: Death Ward, Freedom of Movement, and Holy Sword.
Oh. And Lay on Hands will also heal you for 350 HP... >.>
Edit: Build takes into account corrections now, and properly prioritizes the new holy sword spell over 50 damage.