A Paladin can be a formidable foe. That is, if he's an Avenger. With neither the powerful spells of the Sorceress, Necromancer, and Druid, nor the fighting capabilities of the Barbarian, Amazon, and Assassin, a Paladin has to make do the best he can. By using Vengeance, this holy knight can add Cold, Fire, and Lightning to his melee attack, and with Conviction, he can lower the resistances of his enemies. Interested yet? You should be. By making your Paladin into an Avenger, hell's minions will be bloody dirt beneath your feet.
A level (slvl) 20 Vengeance, with a Mana cost of 8.7, gives you an Attack Rating bonus of 210%, elemental damage of 184%, and the Cold length lasts for 12.6 seconds. The elemental damage is 184% Lightning, 184% Cold, and 184% Fire. (But don't forget that your weapon damage is factored in, too.) Therefore:
If a monster has 50 resist to Cold, then the total elemental damage you do will be decreased by 50 to 502%. But that's what you have Conviction for! With a level (slvl) 20 Conviction, the defense of enemies is lowered by 90%, and their resistance is lowered by 125%. This makes it possible to reduce their resistances below zero, which is definitely a good thing with Vengeance. On a monster with no resists:
I'm not sure how to factor in the physical attack amount, but when you have both these skills at level 20, you're doing damage in the upper thousands. Keep in mind that Conviction's "bonus" to your attack is not shown on your character screen. Instead of boosting your Defense with an aura, bringing down monsters' Defense is just as fun, and other people will love you for it as well!
Most of your character points should go into Vitality. You can never have too much Life, and as a melee character, you'll need it. Second most important is Strength. You'll need it in order to use weapons with lots of damage, and Strength will also add points to the damage that you do. Don't over-do Strength; if you're killing monsters with one hit, you don't need anymore at the moment. You shouldn't put too many points into Mana- you could survive by not putting points into it at all and simply Mana leeching. If you plan to use Fist of the Heavens, a little more Mana is definitely worth it. It's all up to what you prefer. You really need only a few points into Dexterity, besides enough to allow you to use items. If your blocking is extremely low, however, go ahead and put a few points in, but keep in mind that you can use Holy Shield. Also, keep your attack rating at least 75% or higher; you may need more points into Dexterity for that. I suggest you save up at least 20 skill points at the very beginning of the game, so you can use them when you find a good item, or feel you need more skill points into something, instead of waiting for another level-up.
Here's a complete list of what skills you should be using and how many points to put in them, to optimize your Avenger.
Combat Skills
Offensive Auras
Defensive Auras
Sacrifice (1)
Might (1)
Prayer (1)
Smite (1)
Holy Fire (1)
Resist Fire (0)
Holy Bolt (1)
Thorns (1)
Defiance (*)
Zeal (1)
Blessed Aim (*)
Resist Cold (0)
Charge (1)
Concentration (*)
Cleansing (*)
Vengeance (20)
Holy Freeze (*)
Resist Lightning (0)
Blessed Hammer (*)
Holy Shock (0)
Vigor (*)
Conversion (1)
Sanctuary (1)
Meditation (0)
Holy Shield (*)
Fanaticism (0)
Redemption (*)
Fist of the Heavens (*)
Conviction (20)
Salvation (*)
* These skills are needed, not just as pre-requisites, but are recommended, to a certain skill level. More on these skills explained below.
Combat Skills
Everything is a pre-requisite up until Vengeance. Obviously, you want to max out this skill, being an Avenger; enough said. Why should you put points into either Blessed Hammer or Fist of the Heavens? Almost every melee character has problems with large groups of monsters, and the Avenger is no different. It's best to use either Blessed Hammer or Fist of the Heavens, whichever you prefer. However, I recommend using Fist of the Heavens, because it always does more damage, compared to BH. Also, in order to make BH effective, you'd have to put points into Concentration, and that's just too many points wasted.
One more thing about using Fist of the Heavens- with Conviction, you will do even more Lightning damage to your enemies. Its up to you to decide how many points to put into Blessed Hammer / Fist of the Heavens; try it out and see what works best for you. [Suggested amount of skill points to put into Fist of the Heavens: 6] Holy Shield is an absolute must. You won't be putting that much skill points into dexterity, so you'll need a higher blocking rate. If you want to max out your blocking (75%) then put skill points into Holy Shield according to what your shield already provides. However, if you want more Defense, feel free to add more points into it.