Power Attack, definitely. He's already using a two handed weapon, the glaive.
Combat Reflexes and Greater Trip together make for a very effective character, if you have enough Dex to back it up and get multiple AoOs, but that might be too MAD for a paladin.
The paladin in the game I GM has base scores of 16str 10dex (dont remember her con but 14 I think) and 16charisma. She uses a +1 greatsword. Her feats @level 8 are power attack, furious focus, cleave, vital strike, shield of swings. She does quite decent damage.
Her spells are usually swift or immediate action spells such as grace, hero's defiance and paladin's sacrifice (2nd).
Spells she is often buffed with: Bull's Strength, Enlarge, +3 Barkskin (the cleric has this), and Haste.
Divine bond is usually either +2enhancement (stacks with existing enhancements) or holy (+2d6).
She has a cracked Vibrant Purple Ioun Stone (1000gp, seeker of secrets) that stores 1 spell level of spells. The party wizard places a shield spell in it on a regular basis.
When not smiting she does 2d6+17. Enlarged she does 3d6+19 per attack.
When smiting evil critters she does 2d6+25 per attack Enlarged she does 3d6+27.
On occassion she has 1 shoted when combining a critical with a massive damage roll. Her two really big ones were when was smiting an evil creature, shot it with her bow and criticaled. Another major critical she did was over 100pts when using her +1 earthbreaker (2handed blunt weapon, 2d6 20/x3).
- Gauss